COLUMBIA BANCORP
S-4, 1999-12-01
STATE COMMERCIAL BANKS
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<PAGE>

==============================================================================
   As filed with the Securities and Exchange Commission on December 1,1999
                        Securities Act Registration No.
                   Securities Exchange Act Registration No.
==============================================================================

                      SECURITIES AND EXCHANGE COMMISSION

                            Washington, D.C. 20549

                                   FORM S-4

            REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933

                               COLUMBIA BANCORP
                 ---------------------------------------------
            (Exact name of registrant as specified in its charter)

<TABLE>
<CAPTION>
          Maryland                               6022                                         52-1545782
- ------------------------------------------------------------------------------------------------------------------------
<S>                               <C>                                           <C>
(State or other jurisdiction of   (Primary Standard Industrial Classification   (I.R.S. Employer Identification Number)
incorporation or organization)                Code Number)
</TABLE>

           10480 Little Patuxent Parkway, Columbia, Maryland 21044
                                (410) 465-4800
   ------------------------------------------------------------------------
         (Address, including ZIP Code, and telephone number, including
            area code, of registrant's principal executive offices)

                               John M. Bond, Jr.
                     President and Chief Executive Officer
                               Columbia Bancorp
                         10480 Little Patuxent Parkway
                           Columbia, Maryland  21044
                                (410) 465-4800
      ------------------------------------------------------------------
           (Name, address, including ZIP Code, and telephone number,
                  including area code, of agent for service)

                                  Copies to:
          James J. Winn, Jr., Esquire              Stephen C. Hosea, Esquire
     Piper Marbury Rudnick & Wolfe LLP     McNamee, Hosea, Jernigan & Kim, P.A.
         36 South Charles Street                   6411 Ivy Lane, Suite 200
        Baltimore, Maryland  21201               Greenbelt, Maryland  20770
             (410) 539-2530                             (301) 441-2420


     Approximate date of commencement of proposed sale of the securities to the
public: As soon as practicable after the effective date of this Registration
Statement.

     If the securities being registered on this form are being offered in
connection with the formation of a holding company and there is compliance with
General Instruction G, check the following box. [ ]

     If this form is filed to register additional securities for an offering by
Rule 462(b) under the Securities Act, check the following box and list the
Securities Act registration statement number of the earlier effective
registration statement for the same offering. [ ]

     If this form is a post-effective amendment filed by Rule 462(b) under the
Securities Act, check the following box and list the Securities Act registration
statement number of the earlier effective registration statement for the same
offering. [ ]

<TABLE>
<CAPTION>
                                                  Calculation of Registration Fee
======================================================================================================================
Title of each class of                          Proposed maximum        Proposed maximum
   securities to be       Amount to be         offering price per      aggregate offering           Amount of
      registered          registered (1)            share (2)               price (2)         registration fee(2)(3)
======================================================================================================================
<S>                         <C>                 <C>                     <C>                   <C>
Common stock ........       2,642,225                $10.83                $28,606,208               $7,552.39
======================================================================================================================
</TABLE>

(1)    Based upon the maximum number of the registrant's securities that may be
       issued in the merger calculated as the product of (i) the aggregate
       number of shares of Suburban Bancshares common stock outstanding on
       November 3, 1999, and (ii) the maximum conversion ratio of 0.2338 shares
       of the registrant for each share of Suburban Bancshares common stock.

(2)    Estimated solely for the purpose of calculating the registration fee.

(3)    Calculated in accordance with Rule 457(f)(1), on the basis of the average
       of the closing bid and ask price of the common stock of Suburban
       Bancshares on November 30, 1999 of $2.53125 and based on 11,301,218
       shares of Suburban Bancshares common stock to be exchanged in the merger.

                   _________________________________________

       The registrant hereby amends this registration statement on such date or
dates as may be necessary to delay its effective date until the registrant shall
file a further amendment which specifically states that this registration
statement shall thereafter become effective in accordance with Section 8(a) of
the Securities Act of 1933, as amended, or until the registration statement
shall become effective on such date as the Securities and Exchange Commission,
acting pursuant to said Section 8(a), may determine.

<PAGE>

     [LOGO OF SUBURBAN BANCSHARES]            [LOGO OF COLUMBIA BANCORP]

                               ----------------
              YOUR VOTE ON OUR PROPOSED MERGER IS VERY IMPORTANT

Dear Stockholders:

     The directors of Columbia Bancorp and Suburban Bancshares, Inc. have
approved a proposal to merge Suburban Bancshares into Columbia Bancorp.  In the
merger, each share of Suburban Bancshares common stock will be exchanged for
shares of Columbia Bancorp common stock equivalent to an average market value of
$3.00 per share.  The conversion ratio necessary to cause the average market
value of shares of Columbia Bancorp common stock exchanged for each share of
Suburban Bancshares common stock to be $3.00 per share will continually change
until the merger is completed, except that the conversion ratio will not be
above 0.2338 nor below 0.2196.  The conversion ratio represents a value of $___
per share based on the ____________, 1999 price of Columbia Bancorp common
stock.  The market price of Columbia Bancorp common stock will fluctuate prior
to the merger.  In addition, conversion of your shares of Suburban Bancshares
common stock generally will not be taxable.

     The merger will provide Columbia Bancorp and Suburban Bancshares
stockholders with the opportunity to participate in a premier community banking
institution in the Baltimore-Washington area that will result from the
combination of our two companies.  Columbia Bancorp stockholders immediately
prior to the merger initially will own approximately __%, and Suburban
Bancshares stockholders immediately prior to the merger initially will own
approximately __%, of Columbia Bancorp common stock to be outstanding
immediately after the merger.

     Columbia Bancorp common stock is listed on The Nasdaq Stock Market's
National Market under the symbol "CBMD."  Suburban Bancshares common stock is
listed on The Nasdaq Stock Market's SmallCap Market under the symbol "SBNK."

     We believe the merger is a very positive development for both Suburban
Bancshares and Columbia Bancorp.  We are therefore asking for your support in
voting for the merger.  Please take the time to vote by completing and mailing
the enclosed proxy card.  If you do not vote, the effect will be the same as
voting against the merger.

     This proxy statement/prospectus provides you with detailed information
about the proposed merger and the scheduled stockholders' meetings.  We
encourage you to read this entire proxy statement/prospectus carefully.  In
particular, please see the section entitled "Risk Factors" on page 27 of this
proxy statement/prospectus for a discussion of risks associated with the merger.

                               Very truly yours,

     John M. Bond, Jr.                        Winfield M. Kelly, Jr.
     President and Chief Executive Officer    Chairman of the Board and
     Columbia Bancorp                         Chief Executive Officer
                                              Suburban Bancshares, Inc.

- -------------------------------------------------------------------------
          Neither the Securities and Exchange Commission nor any state
     securities commission has approved or disapproved of the
     securities to be issued under this proxy statement/prospectus or
     determined if this proxy statement/prospectus is accurate or
     complete. Any representation to the contrary is a criminal
     offense. The shares of Columbia Bancorp common stock are not
     savings or deposit accounts or other obligations of any bank or
     savings association, and are not insured by the Federal Deposit
     Insurance Corporation or any other governmental agency.
- --------------------------------------------------------------------------
     The date of this proxy statement/prospectus is ______________, 1999, and it
is being mailed or otherwise delivered to stockholders on or about ___________,
1999.
<PAGE>

                               COLUMBIA BANCORP
                         10480 LITTLE PATUXENT PARKWAY
                           COLUMBIA, MARYLAND  21044
                            ______________________

                   NOTICE OF SPECIAL MEETING OF STOCKHOLDERS
                          TO BE HELD __________, 1999

                             ______________________

     A special meeting of stockholders of Columbia Bancorp will be held on
________________, ______, 1999 at the [___________________], beginning at
___:____ __.m. local time, for the following purposes:

     1.  To approve the Plan and Agreement to Merge dated September 28, 1999, as
         amended between Suburban Bancshares, Inc. and Columbia Bancorp and to
         approve the merger of Suburban Bancshares with and into Columbia
         Bancorp as described in the proxy statement/prospectus in which:

         . Suburban Bancshares will be merged with and into Columbia Bancorp,
           with Columbia Bancorp being the surviving corporation;

         . each share of Suburban Bancshares common stock will be exchanged for
           shares of Columbia Bancorp common stock equivalent to an average
           market value of $3.00 per share. The conversion ratio necessary to
           cause the average market value of shares of Columbia Bancorp common
           stock exchanged for each share of Suburban Bancshares common stock to
           be $3.00 per share will continually change until the merger is
           completed, except that the conversion ratio will not be above 0.2338
           nor below 0.2196.; and

         . Suburban Bank of Maryland will be merged with and into The Columbia
           Bank, with The Columbia Bank being the surviving bank.

     2.  To transact such other business as may properly be brought before the
         meeting or any adjournment or postponement of the meeting including
         potential adjournments for the purpose of soliciting additional proxies
         in order to approve and adopt the merger.

     The members of Columbia Bancorp's board of directors have adopted a
resolution unanimously declaring the merger advisable and recommend that
stockholders vote "FOR" approval of the merger.

     We have described the merger in more detail in the proxy
statement/prospectus, which you should read in its entirety before voting.  A
copy of the amended merger agreement is attached as Appendix A to the
accompanying proxy statement/prospectus. Only stockholders of record at the
close of business on ___________________, 1999 are entitled to notice of and to
vote at the meeting or any adjournments or postponements of the meeting.  The
affirmative vote of holders of two-thirds of the Columbia Bancorp common stock
outstanding on ______________, 1999 is necessary to approve the merger.  If that
vote is not obtained, the merger cannot be completed.

     All stockholders are cordially invited to attend the special meeting.  To
ensure your representation at the special meeting please complete and promptly
mail your proxy in the return envelope enclosed.  This will not prevent you from
voting in person, but will help to secure a quorum and avoid added solicitation
costs.  Your proxy may be revoked at any time before it is voted.  If your
shares are not registered in your own name, you will need additional
documentation from the record holder in order to vote personally at the meeting.

                            Your vote is important.

     Whether or not you plan to attend the meeting, please complete, sign, date
and promptly return the enclosed proxy card in the enclosed envelope.

                                    By Order of the Board of Directors


                                    _____________________________________
                                    John A. Scaldara, Jr.
                                    Secretary

Columbia, Maryland

- -----------------------, 1999
<PAGE>

                           SUBURBAN BANCSHARES, INC.
                          7505 Greenway Center Drive
                          Greenbelt, Maryland  20768
                            ______________________

                   NOTICE OF SPECIAL MEETING OF STOCKHOLDERS

                       TO BE HELD _______________, 1999

                            ______________________

     A special meeting of stockholders of Suburban Bancshares, Inc. will be held
on ____________, __________________, 1999 at ________________ beginning  at
__:__ a.m., local time, for the following purposes:

     1.   To approve the Plan and Agreement to Merge dated September 28, 1999,
          as amended, between Suburban Bancshares and Columbia Bancorp and to
          approve the merger of Suburban Bancshares with and into Columbia
          Bancorp as described in the proxy statement/prospectus in which:

        . Suburban Bancshares will be merged with and into Columbia Bancorp,
          with Columbia Bancorp being the surviving corporation;

        . each share of Suburban Bancshares common stock will be exchanged for
          shares of Columbia Bancorp common stock equivalent to an average
          market value of $3.00 per share. The conversion ratio necessary to
          cause the average market value of shares of Columbia Bancorp common
          stock exchanged for each share of Suburban Bancshares common stock to
          be $3.00 per share will continually change until the merger is
          completed, except that the conversion ratio will not be above 0.2338
          nor below 0.2196.; and

        . Suburban Bank of Maryland will be merged with and into The Columbia
          Bank, with The Columbia Bank being the surviving bank.

     2.   To transact such other business as may properly come before the
          meeting or any adjournment or postponement of the meeting including
          potential adjournments for the purpose of soliciting additional
          proxies in order to approve and adopt the merger.

     The members of the Suburban Bancshares' board of directors have unanimously
adopted a resolution declaring the merger advisable and recommend that
stockholders vote "FOR" approval of the merger.

     We have described the merger in more detail in the accompanying proxy
statement/prospectus, which you should read in its entirety before voting.  A
copy of the amended merger agreement is attached as Appendix A to the proxy
statement/prospectus.  Only stockholders of record at the close of business on
_________________, 1999 are entitled to notice of and to vote at the meeting or
any adjournment or postponement of the meeting.  The affirmative vote of holders
of a majority of the Suburban Bancshares common stock outstanding on
_____________________, 1999 is necessary to approve the merger.  If that vote is
not obtained, the merger cannot be completed.

     All stockholders are cordially invited to attend the special meeting.  To
ensure your representation at the special meeting please complete and promptly
mail your proxy in the return envelope enclosed.  This will not prevent you from
voting in person, but will help to secure a quorum and avoid added solicitation
costs.  Your proxy may be revoked at any time before it is voted.  If your
shares are not registered in your own name, you will need additional
documentation from the record holder in order to vote personally at the meeting.

                            Your vote is important.

     Whether or not you expect to attend the meeting in person, please complete,
sign, date and promptly return the enclosed proxy card in the enclosed postage-
paid envelope.

                                     By Order of the Board of Directors

                                     ___________________________
                                     Susan J. Hansen
                                     Secretary

Greenbelt, Maryland
______________, 1999
<PAGE>

                               TABLE OF CONTENTS

<TABLE>

<S>                                                                                                               <C>
     QUESTIONS AND ANSWERS ABOUT  THE MERGER......................................................................1

     SUMMARY......................................................................................................4

     SELECTED HISTORICAL AND PRO FORMA CONSOLIDATED FINANCIAL DATA...............................................12

     FORWARD-LOOKING STATEMENTS..................................................................................20

     RISK FACTORS................................................................................................25

     GENERAL INFORMATION ABOUT THE MEETINGS......................................................................31
         Date, Time and Place of the Meetings....................................................................31
         Record Date and Outstanding Shares......................................................................31
         Purpose of the Meetings.................................................................................31
         Vote Required...........................................................................................32
         Voting of Proxies.......................................................................................34
         Authorization to Vote on Adjournment and Other Matters..................................................34
         Revocation of Proxies...................................................................................35
         Solicitation of Proxies.................................................................................36

     PARTIES TO THE MERGER.......................................................................................37
         Columbia Bancorp........................................................................................37
         Suburban Bancshares.....................................................................................38

     THE MERGER..................................................................................................40
         Background of the Merger................................................................................40
         Suburban Bancshares Reasons for the Merger..............................................................42
         Opinion of Suburban Bancshares'Financial Advisor........................................................44
         Balance Sheet...........................................................................................47
         Stock Price.............................................................................................47
         Columbia Bancorp Reasons for the Merger.................................................................48
         Opinion of Columbia Bancorp's Financial Advisor.........................................................49
         Interests of Persons in the Merger Other Than as Stockholders...........................................52
         Form of the Merger......................................................................................54
         Consideration for the Merger............................................................................54
         Effective Time of the Merger............................................................................55
         Procedures for Exchange of Suburban Bancshares Stock Certificates.......................................55
         Exchange of Suburban Bancshares Stock Options...........................................................56
         Anticipated Accounting Treatment........................................................................56
         Material Federal Income Tax Considerations..............................................................57
</TABLE>
                                      -i-
<PAGE>

<TABLE>

<S>                                                                                                              <C>
         Regulatory Approvals Required...........................................................................59
         Nasdaq Stock Market Listing.............................................................................60
         Appraisal Rights........................................................................................60
         Resale of Columbia Bancorp Common Shares After the Merger...............................................63

     THE MERGER AGREEMENT........................................................................................65
         General.................................................................................................65
         Conversion Ratios; Fractional Shares....................................................................65
         Certain Representations and Warranties..................................................................65
         Certain Covenants and Agreements........................................................................67
         Conditions to the Merger................................................................................69
         Termination.............................................................................................71
         Amendment; Waiver.......................................................................................72
         Expenses................................................................................................73

     STOCK OPTION AGREEMENTS.....................................................................................74
         General.................................................................................................74
         Exercise; Expiration....................................................................................74
         Registration Rights.....................................................................................75
         Purpose of the Agreements...............................................................................76

     Support Agreements..........................................................................................76

     Certain Information Incorporated by Reference...............................................................77

     COMPARISON OF THE RIGHTS OF HOLDERS OF COLUMBIA BANCORP CAPITAL STOCK AND SUBURBAN BANCSHARES
     CAPITAL STOCK...............................................................................................78
         General.................................................................................................96
         Common Stock............................................................................................96
         Preferred Stock.........................................................................................96

     FUTURE STOCKHOLDER PROPOSALS................................................................................98

     OTHER MATTERS...............................................................................................98

     LEGAL MATTERS...............................................................................................99

     EXPERTS.....................................................................................................99

     Appendix A AGREEMENT AND PLAN OF MERGER....................................................................A-1

     Appendix B SUPPORT AGREEMENT OF COLUMBIA BANCORP...........................................................B-1

     Appendix C SUPPORT AGREEMENT OF SUBURBAN BANCSHARES........................................................C-1

     Appendix D COLUMBIA BANCORP STOCK OPTION AGREEMENT.........................................................D-1
</TABLE>
                                     -ii-
<PAGE>

<TABLE>

<S>                                                                                                               <C>
     Appendix E SUBURBAN BANCSHARES STOCK OPTION AGREEMENT........................................................ E-1

     Appendix F OPINION OF AUSTIN FINANCIAL....................................................................... F-1

     Appendix G OPINION OF DANIELSON ASSOCIATES................................................................... G-1

     Appendix H SECTION 262 OF THE DELAWARE GENERAL CORPORATION LAW............................................... H-1
</TABLE>

                                     -iii-
<PAGE>

                          QUESTIONS AND ANSWERS ABOUT
                                  THE MERGER

Q:   What should I do?

A:   After you have carefully read this proxy statement/prospectus, mail your
     signed proxy card in the enclosed envelope. The instructions on the
     accompanying proxy card will give you more information on how to vote by
     mail. This will enable your shares to be represented at the Columbia
     Bancorp special meeting or the Suburban Bancshares special meeting, as
     applicable. If you fail to return a proxy card or abstain from voting, the
     effect will be a vote against the merger.

Q:   If my shares are held in "street name" by my broker, will my broker vote my
     shares for me?

A:   Maybe. Your broker will not be able to vote your shares without
     instructions from you. You should instruct your broker to vote your shares,
     following the directions your broker provides. Your failure to instruct
     your broker to vote your shares will result in your shares not being voted,
     and the affect will be a vote against the merger.

Q:   Can I change my vote after I have submitted my proxy with voting
     instructions?

A:   Yes. There are three ways you can change your vote. First, you may send a
     written notice to the person to whom you submitted your proxy stating that
     you would like to revoke your proxy. Second, you may complete and submit a
     new proxy card by mail or submit your proxy with new voting instructions.
     The vote dated latest and actually received by Suburban Bancshares or
     Columbia Bancorp prior to the stockholders' meeting will be your vote. Any
     earlier votes will be revoked. Third, you may attend the Columbia Bancorp
     special meeting or the Suburban Bancshares special meeting, as applicable,
     and vote in person. Any earlier votes will be revoked. Simply attending the
     meeting without voting, however, will not revoke your proxy. If you have
     instructed a broker to vote your shares, you must follow directions you
     will receive from your broker to change or revoke your proxy.

Q:   What will I receive in the merger?

A:   Each share of Suburban Bancshares common stock will be exchanged for shares
     of Columbia Bancorp common stock equivalent to an average market value of
     $3.00 per share. The conversion ratio necessary to cause the average market
     value of shares of Columbia Bancorp common stock exchanged for each share
     of Suburban Bancshares common stock to be $3.00 per share will continually
     change until the merger is completed, except that the conversion ratio will
     not be above 0.2338 nor below 0.2196. If you have options to purchase
     shares of Suburban Bancshares common stock, whether vested or unvested,
     they will be converted into an option to purchase shares of Columbia
     Bancorp common stock and will no longer represent a right to acquire shares
     of Suburban Bancshares common stock. Columbia Bancorp common stock is
     publicly traded on the Nasdaq National Market under the symbol "CBMD." The
     merger will not have an effect on the Columbia Bancorp common stock. Of
     course, the number of shares of Columbia Bancorp common stock outstanding
     will increase from approximately 4.5 million shares to approximately 7.1
     million shares.

                                      -1-
<PAGE>

Q:   Should I send in my stock certificates?

A:   No. You should not send in your stock certificates at this time. Columbia
     Bancorp stockholders will not exchange their certificates in the merger.
     The certificates currently representing the shares of Columbia Bancorp
     common stock will continue to represent the same number of shares of
     Columbia Bancorp common stock after the merger.

     Suburban Bancshares stockholders will exchange their Suburban Bancshares
     common stock certificates for Columbia Bancorp common stock certificates
     after we complete the merger. Instructions for exchanging Suburban
     Bancshares common stock certificates will be sent to you promptly after the
     merger is completed.

Q:   Who should I call if I have questions?

A:   Columbia Bancorp stockholders should call John A. Scaldara, Jr., at (410)
     465-4800 with any questions about the merger and the related transactions.

     Suburban Bancshares stockholders should call Stephen A. Horvath at (301)
     474-6694.

Q:   What vote is required to approve the merger?

A:   In order to complete the merger, holders of two-thirds of the outstanding
     shares of Columbia Bancorp common stock and holders of a majority of the
     outstanding shares of Suburban Bancshares common stock must approve the
     merger.

Q:   What effect will dissenting stockholders seeking appraisal rights have on
     the merger?

A.   The merger will not be completed unless Columbia Bancorp receives a letter
     from KPMG LLP that the merger will qualify for pooling-of-interests
     accounting treatment. If the number of Suburban Bancshares stockholders who
     have demanded appraisal rights and not withdrawn those demands jeopardizes
     the qualification of the merger for pooling-of-interests accounting
     treatment and KPMG LLP fails or refuses to deliver a letter to Columbia
     Bancorp to that effect, then Columbia Bancorp has the right to terminate
     the merger agreement and the merger will not close. Furthermore, we cannot
     assure you that if you seek appraisal of your shares of Suburban Bancshares
     common stock that you will receive a higher price valuation than is being
     offered in the merger.

Q:   When do you expect to complete the merger?

A.   We are working toward completing the merger as quickly as possible. We must
     first obtain the approval of Suburban Bancshares common stockholders at the
     Suburban Bancshares special meeting, the approval of Columbia Bancorp
     common stockholders at the Columbia Bancorp special meeting and approvals
     from state and federal bank regulators. We will file applications with the
     Federal Deposit Insurance Corporation ("FDIC"), the Federal Reserve Board
     and the Maryland Commissioner of Financial Regulation. The stockholder
     meetings are scheduled for __________, 1999. We hope to complete the merger
     shortly after that date.

                                      -2-
<PAGE>

Q:   Will I receive dividends on my Columbia Bancorp shares before the merger?

A.   The merger agreements permits Columbia Bancorp to pay, prior to the
     closing, regular quarterly cash dividends to its stockholders.

Q:   Where can I find more information about the companies?

A.   Both companies file reports and other information with the Securities and
     Exchange Commission ("SEC"). You may read and copy this information at the
     SEC's public reference facilities. Please call the SEC at 1-800-SEC-0330
     for information about these facilities. This information is also available
     at the Internet site the SEC maintains at www.sec.gov. You can also request
     copies of these documents from us. See "Where You Can Find More
     Information" on page 101.

                                      -3-
<PAGE>

                                    SUMMARY
     This summary highlights selected information from this proxy
statement/prospectus and may not contain all of the information that is
important to you. To understand the merger fully, you should read carefully the
entire proxy statement and the other documents attached to this proxy statement.
The amended merger agreement is attached as Appendix A to this proxy statement.
For more information about the two companies, see "Where You Can Find More
Information" (page 101). For your reference, we have included page references to
direct you to more complete descriptions of the topics presented in this
summary.

The Companies

Columbia Bancorp
10480 Little Patuxent Parkway
Columbia, Maryland  21044
(410) 465-4800

     Columbia Bancorp is a registered bank holding company organized in 1987 as
a Maryland corporation that began its operations in 1988. Columbia Bancorp's
principal subsidiary is Columbia Bank, a commercial bank headquartered in
Columbia, Maryland. On September 30, 1999, Columbia Bancorp had total
consolidated assets of $460.1 million, total consolidated deposits of $354.0
million, stockholders' equity of $39.9 million and net income of $3.9 million
for the first nine months of 1999. Columbia Bancorp offers a broad range of bank
and bank-related services through Columbia Bank, which constitutes approximately
100% of the consolidated assets of Columbia Bancorp.

     Columbia Bank is a commercial bank organized under the laws of the State of
Maryland. Columbia Bank has banking branches in Howard and Baltimore Counties
and Baltimore City.

     As of October 31, 1999, there were 4,506,035 shares of Columbia Bancorp
common stock issued and outstanding.  Columbia Bancorp common stock is quoted on
the Nasdaq National Market under the symbol "CBMD."  For additional information
about Columbia Bancorp, its business, financial condition, and operations see
39.

Suburban Bancshares, Inc.
7505 Greenway Center Drive
P.O. Box 298
Greenbelt, Maryland  20768
(301) 474-6694

     Suburban Bancshares is a registered bank holding company organized in 1985
as a Delaware corporation. Suburban Bancshares' sole subsidiary is Suburban
Bank, a commercial bank headquartered in Greenbelt, Maryland. As of and for the
nine months ended September 30, 1999, Suburban Bancshares had total consolidated
assets of $222.8 million, total deposits of $187.7 million, stockholders' equity
of $20.4 million, and net income of $710,000. Suburban Bancshares offers a broad
range of bank and bank-related services through Suburban Bank.

     Suburban Bank is a commercial bank organized under the laws of the State of
Maryland.  Suburban Bank has branches in Montgomery and Prince George's
Counties.


                                      -4-
<PAGE>

     As of November 3, 1999, there were 11,301,218 shares of Suburban Bancshares
common stock issued and outstanding. Suburban Bancshares common stock is quoted
on the Nasdaq SmallCap Market under the symbol "SBNK." For additional
information about Suburban Bancshares, its business, financial condition, and
operations see 40.

The Merger

     The amended merger agreement is attached to this proxy statement/prospectus
as Appendix A. We encourage you to read the merger agreement as it is the legal
document that governs the merger between Columbia Bancorp and Suburban
Bancshares.

     Upon completion of the merger, Suburban Bancshares will merge into Columbia
Bancorp, and Suburban Bancshares will cease to exist as a separate company.  As
part of the merger, Columbia Bancorp and Suburban Bancshares will cause Suburban
Bank to merge into Columbia Bank pursuant to a plan of bank merger.  We expect
to complete the bank merger concurrently with the completion of the merger.

Shares of Suburban Bancshares Common Stock Will Be Exchanged for Shares of
Columbia Bancorp Common Stock Equivalent to a Market Value of $3.00 Per Share
(page 56)

     If the merger is completed, you will receive the number of shares of
Columbia Bancorp common stock for each share of Suburban Bancshares common stock
you own, plus cash instead of any fractional share, based on a conversion ratio
to cause the average market value to be $3.00 per share. The conversion ratio
necessary to cause the average market value of shares of Columbia Bancorp common
stock exchanged for each share of Suburban Bancshares common stock to be $3.00
per share will continually change until the merger is completed, except that the
conversion ratio will not be above 0.2338 nor below 0.2196. On ________________,
1999, the closing price of Columbia Bancorp common stock was $_______, making
the value of ________ shares of Suburban Bancshares common stock equal to
$__________ on that date. Because the market price of Columbia Bancorp common
stock fluctuates, you will not know when you vote what the shares will be worth
when issued in the merger.

Meetings to be Held ____________, 1999; Record Dates (page 33)

     The Columbia Bancorp meeting will be held at _:___ __.m. on _________, 1999
at the [_________________________]. At the Columbia Bancorp meeting, Columbia
Bancorp stockholders will be asked to consider and vote on a proposal to approve
the merger by approving and adopting the merger agreement. If you held shares of
Columbia Bancorp common stock at the close of business on ______________, 1999,
you are entitled to vote on the merger, and any other matters considered at the
Columbia Bancorp meeting or any adjournment or postponement of the meeting.

     The Suburban Bancshares meeting will be held at __:00 a.m. on _________,
1999 at ________ _______________________________. At the Suburban Bancshares
meeting, Suburban Bancshares stockholders will be asked to consider approving
the merger by approving and adopting the merger agreement. If you held shares of
Suburban Bancshares common stock at the close of business on _______________,
1999, you are entitled to vote on the merger and any other matters considered at
the Suburban Bancshares meeting or any adjournment or postponement of the
meeting.

                                      -5-
<PAGE>

Required Vote (page 34)

     Two-thirds of the outstanding shares of Columbia Bancorp common stock
entitled to be voted at the Columbia Bancorp meeting must vote in favor of the
proposal to approve the merger by approving and adopting the merger agreement in
order for the merger to be approved. Each share is entitled to one vote on each
matter to be voted on at the Columbia Bancorp meeting. All directors and
executive officers of Columbia Bancorp have executed a support agreement to vote
all of the shares of Columbia Bancorp common stock which they beneficially own
in favor of the merger. As of September 30, 1999, directors and executive
officers of Columbia Bancorp and their affiliates beneficially owned 979,698
shares of Columbia Bancorp common stock, which represented 21.7% of the
4,506,035 Columbia Bancorp common stock outstanding on that date.

     A majority of the outstanding shares of Suburban Bancshares common stock
entitled to be voted at the Suburban Bancshares meeting must vote in favor of
the proposal to approve the merger by approving and adopting the merger
agreement in order for the merger to be approved. Each share is entitled to one
vote on each matter to be voted on at the Suburban Bancshares meeting. All
directors and executive officers of Suburban Bancshares have executed a support
agreement to vote all of the shares of Suburban Bancshares common stock which
they beneficially own in favor of the merger. As of September 30, 1999,
directors and executive officers of Suburban Bancshares and their affiliates
beneficially owned 2,263,091 shares of Suburban Bancshares common stock, which
represented 20.0% of the outstanding Suburban Bancshares common stock
outstanding at that date.

Columbia Bancorp and Suburban Bancshares Boards Recommend Stockholder Approval
(page 40 and page 50)

     The Columbia Bancorp board of directors is of the opinion that the merger
is advisable and in the best interests of Columbia Bancorp and the Columbia
Bancorp stockholders. The members of the Columbia Bancorp board of directors
unanimously approved the merger agreement and the merger and recommend that
Columbia Bancorp stockholders vote FOR the proposal to approve the merger
agreement and the merger.

     The Suburban Bancshares board of directors has determined that the merger
is advisable and in the best interests of Suburban Bancshares and its
stockholders. The members of the Suburban Bancshares board of directors
unanimously approved the merger agreement and the merger and recommend that
Suburban Bancshares stockholders vote FOR approval of the merger agreement and
the merger.

                                      -6-
<PAGE>

Consideration to be Paid by Columbia Bancorp Fair to Stockholders, According to
Financial Advisors (page 46 and page 51)

     In deciding to approve the merger, the Columbia Bancorp board of directors
received and considered the opinion dated September 24, 1999 of Austin Financial
Services, Inc., its financial advisor, as to the fairness to the Columbia
Bancorp stockholders of the share conversion ratio from a financial point of
view as of that date. The opinion of Austin Financial does not constitute a
recommendation as to how any Columbia Bancorp stockholder should vote with
respect to the proposal to approve the merger. You should read the opinion in
its entirety to understand the assumptions made, matters considered and
limitations of the review undertaken by Austin Financial in providing its
opinion. A copy of Austin Financial's opinion is attached to the proxy
statement/prospectus as Appendix F. Austin Financial will receive total fees of
approximately $17,500 for its services as financial advisor to Columbia Bancorp
in connection with the merger.

     In deciding to approve the merger, the Suburban Bancshares board of
directors received and considered the opinion dated September 28, 1999 of
Danielson Associates, Inc., its financial advisor, as to the fairness to the
Suburban Bancshares stockholders of the share conversion ratio from a financial
point of view as of that date. The opinion of Danielson Associates does not
constitute a recommendation as to how any Suburban Bancshares stockholder should
vote with respect to the proposal to approve the merger. You should read the
opinion in its entirety to understand the assumptions made, matters considered
and limitations of the review undertaken by Danielson Associates in providing
its opinion. A copy of Danielson Associates' opinion is attached to the proxy
statement/prospectus as Appendix G. Danielson Associates will receive total fees
of approximately $169,500 for its services as financial advisor to Suburban
Bancshares in connection with the merger.

Benefits to Certain Suburban Bancshares Officers and Directors in the Merger
(page 54)

     Suburban Bancshares' directors and certain officers have interests in the
merger that are different from your and their interests as stockholders.

     These interests include, among other things:

     .  Columbia Bancorp will enter into an employment agreement with Mr.
        Horvath;

     .  five directors of Suburban Bancshares will be appointed to the
        Columbia Bancorp board of directors;

     .  Columbia Bancorp will enter into a services agreement with Mr. Kelly
        which is similar to his current services agreement with Suburban
        Bancshares and provides for Mr. Kelly to serve as the Chairman of the
        Board of the Columbia Bancorp board of directors and to receive a
        payment of additional compensation of $200,000 upon the earlier of five
        years from the date of his services agreement or upon a change in
        control.

Conditions to the Merger (page 71)

     The merger will not be completed unless we satisfy several conditions,
including:

     .  approval of the merger by Columbia Bancorp stockholders and Suburban
        Bancshares stockholders;
     .  the absence of legal restraints that prevent the completion of the
        merger;

                                      -7-
<PAGE>

     .  receipt of a legal opinion from Columbia Bancorp's legal counsel
        that the merger will be tax-free, except for any cash received in lieu
        of fractional shares or by dissenters;
     .  the continuing accuracy of our representations in the merger agreement;
     .  the continuing effectiveness of the registration statement filed with
        the SEC; and
     .  the receipt of certain bank regulatory approvals.

     In addition, the merger will not be completed unless Columbia Bancorp
receives a letter from KPMG LLP that the merger will qualify for pooling-of-
interests accounting treatment.

     We may not waive any conditions that are required by law to complete the
merger, including the requirements for stockholder approval, the requirements
for regulatory approval and that the registration statement be effective on the
closing date of the merger. Unless prohibited by law, either Columbia Bancorp or
Suburban Bancshares could waive a condition that has not been satisfied and
complete the merger. Neither Columbia Bancorp nor Suburban Bancshares intends to
waive any material condition to the merger.

Termination and Amendment of the Merger Agreement (page 73 and page 74)

     We can mutually agree at any time to terminate the merger agreement without
completing the merger. Either company can also terminate the merger agreement
if, among other reasons:

     .  any government or court issues an order or takes another action
        enjoining or prohibiting the merger;

     .  any required approval, consent or waiver is denied;

     .  the other party materially breaches any of its representations,
        warranties or agreements under the merger agreement or the merger, and
        such breach is not cured within 60 days or cannot be cured by June 30,
        2000;

     .  if any government's or court's approval, consent or waiver is
        conditioned on a requirement that would have a material adverse effect
        on Columbia Bancorp or Suburban Bancshares or would materially
        adversely affect the benefits of the merger; or

     .  either company fails to obtain stockholder approval.

     At any time prior to the completion of the merger, we may amend the merger
agreement in any way. On November 24, 1999 we amended the merger agreement to
provide for the effects of dissenting stockholders. Once the merger agreement is
approved by stockholders of either company, any amendment must be approved by
Columbia Bancorp stockholders if this approval is required under Maryland law
and by Suburban Bancshares stockholders if this approval is required under
Delaware law.

Regulatory Approvals We Must Obtain for the Merger (see page 61)

     We cannot complete the merger unless it is approved by the FDIC. We will
file applications with the FDIC seeking its approval. In addition, the merger is
subject to the approval of or notice to certain

                                      -8-
<PAGE>

other federal and state and other regulatory authorities. We will also make the
necessary filings with these other regulatory authorities.

     Although we do not know of any reason why we cannot obtain these regulatory
approvals in a timely manner, we cannot be certain that we will obtain them, or
when we will obtain them.

Columbia Bancorp Will Be Required to Issue 497,140 Shares of Columbia Bancorp
Common Stock to Suburban Bancshares Under Certain Circumstances if the Merger Is
Not Completed (see page 76)

     In connection with the merger agreement, Columbia Bancorp granted Suburban
Bancshares an option to purchase 497,140 shares of Columbia Bancorp common
stock. Under this option, Suburban Bancshares may purchase up to the equivalent
of 9.9% of the outstanding shares of Columbia Bancorp common stock, assuming the
option is exercised, at a price per share of $13.063.

     Suburban Bancshares cannot exercise this option unless certain events occur
within a specified time period. These events can generally be described as
business combinations or acquisition transactions relating to Columbia Bancorp
and certain related events (other than the merger we are proposing in this proxy
statement/prospectus). We do not know of any event that has occurred as of the
date of this proxy statement/prospectus that would allow Suburban Bancshares to
exercise this option.

     Columbia Bancorp agreed to grant this option to Suburban Bancshares in
order to induce Suburban Bancshares to enter into the merger agreement. This
option could have the effect of discouraging other companies from trying to
acquire Columbia Bancorp until the merger is completed.

     This option agreement is attached to this proxy statement/prospectus as
Appendix D.

Suburban Bancshares Will Be Required to Issue 2,807,668 Shares of Suburban
Bancshares Common Stock to Columbia Bancorp Under Certain Circumstances if the
Merger Is Not Completed (see page 76)

     In connection with the merger agreement, Suburban Bancshares granted
Columbia Bancorp an option to purchase 2,807,668 shares of Suburban Bancshares
common stock. Under this option, Columbia Bancorp may purchase up to the
equivalent of 19.9% of the outstanding shares of Suburban Bancshares common
stock, assuming the option is exercised, at a price per share of $2.313.

     Columbia Bancorp cannot exercise this option unless certain events occur
within a specified time period. These events can generally be described as
business combinations or acquisition transactions relating to Suburban
Bancshares and certain related events (other than the merger we are proposing in
this proxy statement/prospectus). We do not know of any event that has occurred
as of the date of this proxy statement/prospectus that would allow Columbia
Bancorp to exercise this option.

     Suburban Bancshares agreed to grant this option to Columbia Bancorp in
order to induce Columbia Bancorp to enter into the merger agreement. This option
could have the effect of discouraging other companies from trying to acquire
Suburban Bancshares.

     This option agreement is attached to this proxy statement/prospectus as
Appendix E.

                                      -9-
<PAGE>

Columbia Bancorp to Use Pooling-of-Interests Accounting Treatment (page 58)

     We expect the merger to qualify as a pooling-of-interests, which means that
both companies will be treated as if they had always been combined for
accounting and financial reporting purposes. Generally, pooling-of-interests
accounting treatment enhances future earnings by avoiding the creation of
goodwill relating to the merger. Therefore, Columbia Bancorp should be able to
avoid charges against future earnings resulting from the amortization of
goodwill which would have been created if this accounting treatment were not
used. We have conditioned the merger upon the receipt of a letter from KPMG LLP,
the independent public accountants of Columbia Bancorp, stating their opinion
that the merger will qualify for pooling-of-interests accounting treatment.
Columbia Bancorp has the right to terminate the merger agreement and be released
from all obligations if, immediately prior to the effective date, the number of
Suburban Bancshares stockholders who have demanded appraisal rights and not
withdrawn those demands jeopardizes the qualification of the merger for pooling-
of-interests accounting treatment and KPMG LLP fails or refuses to deliver a
letter to Columbia Bancorp to that effect.

Dissenters' Rights of Appraisal (page 62)

     If the merger is completed, Suburban Bancshares stockholders who do not
vote for the adoption of the merger agreement and who otherwise comply with
Section 262 of the Delaware General Corporation Law will be entitled to
appraisal rights under Delaware law. Columbia Bancorp has the right to terminate
the merger agreement and be released from all obligations if, immediately prior
to the effective date, the number of Suburban Bancshares stockholders who have
demanded appraisal rights and not withdrawn those demands jeopardizes the
qualification of the merger for pooling-of-interests accounting treatment and
KPMG LLP fails or refuses to deliver a letter to Columbia Bancorp to that
effect.  A copy of Section 262 of the Delaware General Corporation Law is
attached as Appendix H.

     Columbia Bancorp stockholders do not have appraisal rights in connection
with the merger.

Listing of Columbia Bancorp Common Shares (page 62)

     Columbia Bancorp common stock is traded on The Nasdaq National Market under
the symbol "CBMD."  Columbia Bancorp will list the additional shares of common
stock to be issued in the merger on The Nasdaq National Market.

No Federal Income Tax on Shares Received in the Merger (page 58)

     As a condition to the merger, we will receive an opinion of Columbia
Bancorp's tax counsel concluding, among other things, that no gain or loss
generally will be recognized by a Suburban Bancshares stockholder for federal
income tax purposes on the exchange of shares of Suburban Bancshares common
stock for shares of Columbia Bancorp common stock, except in connection with any
cash received in lieu of fractional shares or by dissenting stockholders.

     Tax matters are very complicated and the tax consequences of the merger to
you will depend on your personal circumstances.  We urge you to consult your own
tax advisors to understand fully the tax consequences to you.

                                      -10-
<PAGE>

A Warning About Forward-Looking Statements (page 22)

     We make statements in this proxy statement/prospectus and in the documents
delivered and incorporated by reference that are forward-looking. You can
identify these statements by our use of words like "may," "will," "expect,"
"anticipate," "estimate," or "continue," or similar expressions. Forward-looking
statements represent our judgment about the future and are not guarantees of our
future performance. Certain risks and uncertainties could cause our actual
operating results and financial position to differ materially from our
projections. We caution you not to place undue reliance on forward-looking
statements. Such forward-looking statements represent our estimates and
assumptions only as of the date of this proxy statement/prospectus.

Share Information and Market Prices

     Columbia Bancorp common stock is traded on The Nasdaq National Market under
the symbol "CBMD." Suburban Bancshares common stock is traded on The Nasdaq
SmallCap Market under the symbol "SBNK". The following table shows, for the
periods indicated, the last sale prices per share of Columbia Bancorp and
Suburban Bancshares common stock, and the equivalent merger consideration per
share of Suburban Bancshares common stock on September 28, 1999, the last
trading day before we announced merger, and on ________________, 1999, the
latest practicable date before we mailed this proxy statement/prospectus.

<TABLE>
<CAPTION>
                                                                                             Value of
                                                                                              Merger
                                                                                          Consideration
                                                      Columbia          Suburban           Per Share of
                                                      Bancorp          Bancshares      Suburban Bancshares
                                                     Common Stock     Common Stock        Common Stock
                                                     ------------     ------------        ------------

<S>                                                  <C>              <C>              <C>
September 28, 1999..............................     $12.81           $2.19            $3.00/(1)/
____________, 1999..............................     $                $                $    /(2)/
</TABLE>
________________

(1) If the average market value of the Columbia Bancorp common stock was
    $12.81, the conversion ratio would be 0.2338.
(2) If the average market value of the Columbia Bancorp common stock was $____,
    the conversion ratio would be ___.

     The market prices of both Columbia BAncorp and Suburban Bancshares common
stock will fluctuate prior to the merger. You should obtain current market
quotations for Columbia Bancorp common stock and Suburban Bancshares common
stock. Following the merger, shares of Columbia Bancorp common stock will
continue to be traded on the Nasdaq National Market.

     As of October 31, 1999, there were approximately 2,100 beneficial owners of
shares of Columbia Bancorp common stock, including 320 holders of record. As of
October 31, 1999, there were approximately 1,118 beneficial and 881 record
owners of Suburban Bancshares common stock.

                                      -11-
<PAGE>

         SELECTED HISTORICAL AND PRO FORMA CONSOLIDATED FINANCIAL DATA

Columbia Bancorp

     Columbia Bancorp's selected historical data is based on its Annual Report
on Form 10-K for the year ended December 31, 1998, its Quarterly Report on Form
10-Q for the quarter ended September 30, 1999 and other financial information
incorporated by reference in and delivered with this proxy statement/prospectus.
You should read this financial information in conjunction with the information
in those Columbia Bancorp reports and other information incorporated by
reference in this proxy statement/prospectus. See "Where You Can Find More
Information" on page 101.

                                      -12-
<PAGE>

                        COLUMBIA BANCORP AND SUBSIDIARY
                     CONDENSED CONSOLIDATED FINANCIAL DATA

<TABLE>
<CAPTION>
                                                                                                             As of or for
                                                                                                           the Nine Months
                                                As of or for the Year Ended December 31,                 Ended September 30,
                                   ----------------------------------------------------------------     --------------------
                                     1994          1995          1996          1997          1998         1998         1999
                                   --------      --------      --------      --------      --------     --------    --------
                                                                  (dollars in thousands, except per share data)
<S>                                <C>           <C>           <C>           <C>           <C>          <C>         <C>
Consolidated Income Statement:
   Interest income                 $ 17,031      $ 22,210      $ 25,822      $ 30,194      $ 32,928     $ 24,708    $ 25,195
   Interest expense                   5,705         7,892         8,769        11,473        13,018        9,706       9,492
                                   ------------------------------------------------------------------   --------------------
   Net interest income               11,326        14,318        17,053        18,721        19,910       15,002      15,703
   Provision for credit losses          242           559           621           663           659          517         290
                                   ------------------------------------------------------------------   --------------------
   Net interest income after
   Provision for credit losses       11,084        13,759        16,432        18,058        19,251       14,485      15,413
   Noninterest income                 1,504         1,300         1,788         2,182         3,424        2,421       2,569
   Noninterest expense                8,649         9,472        12,081        13,722        15,384       11,455      12,073
                                   ------------------------------------------------------------------   --------------------
   Income before income taxes         3,939         5,587         6,139         6,518         7,291        5,451       5,909
   Income taxes                       1,523         2,158         2,387         2,350         2,545        1,910       2,042
                                   ------------------------------------------------------------------   --------------------
   Net income                      $  2,416      $  3,429      $  3,752      $  4,168      $  4,746     $  3,541    $  3,867
                                   ------------------------------------------------------------------   --------------------
Consolidated Balance Sheet (at
 period-end):
   Assets:
     Cash and cash equivalents     $ 13,527      $ 28,092      $ 21,231      $ 15,511      $ 32,529     $ 39,068    $ 24,380
     Securities, including those     38,279        35,341        44,149        66,645        84,016       76,721     109,719
     available-for-sale
     Loans originated for sale          460         1,045         1,551         6,557        17,387       11,732       2,994
     Loans, net of unearned income   162,253      190,691       237,875       265,194       274,413      268,215     305,339
     Allowance for credit losses      (2,578)      (2,929)       (3,293)       (3,632)       (3,965)      (3,907)     (4,227)
     Other assets                     12,267       10,785        15,721        23,176        22,955       23,260      21,882
                                   ------------------------------------------------------------------   --------------------
   Total assets                    $224,208      $263,025      $317,234      $373,451      $427,335     $415,089    $460,087
                                   ------------------------------------------------------------------   --------------------

   Liabilities and Equity:
     Deposits                      $189,463      $218,162      $254,640      $313,357      $339,336     $330,672    $354,024
     Short-term borrowings           16,896        15,299        30,127        23,725        27,012       29,088      43,660
     Long-term borrowings                 -             -             -             -        20,000       15,000      20,000
     Other liabilities                  976         1,500         1,492         1,984         2,633        2,579       2,492
     Stockholders' equity            16,873        28,064        30,975        34,385        38,354       37,750      39,911
                                   ------------------------------------------------------------------   --------------------
   Total liabilities and equity    $224,208      $263,025      $317,234      $373,451      $427,335     $415,089    $460,087
                                   ------------------------------------------------------------------   --------------------

Per Share Data (a):
   Number of shares of Common
   Stock
   Outstanding (in thousands)         2,080         4,292         4,296         4,400         4,562        4,572       4,506
   Net income:
     Basic                         $   0.90      $   1.03      $   0.87      $   0.96      $   1.05     $   0.78    $   0.86
     Diluted                           0.79          0.90          0.83          0.91          1.03         0.77        0.84
   Cash dividends declared:
     Common                            0.07          0.13          0.21          0.25          0.29         0.21        0.24
     Preferred                         1.20          1.30             -             -             -            -           -
   Tangible book value                 5.81          6.46          7.15          7.77          8.39         8.23        8.85
Performance and Capital Ratios:
   Return on average assets            1.13%         1.42%         1.34%         1.21%         1.18%        1.20%       1.17%
   Return on average
   stockholders' equity               15.01         15.60         12.71         12.78         12.94        13.09       13.24
   Net interest margin (b)             5.90          6.46          6.60          5.99          5.40         5.55        5.15
   Average stockholders' equity to
   Average total assets                7.53          9.07         10.53          9.44          9.09         9.14        8.82
   Period-end capital to
   period-end
     Risk-weighted assets:
     Tier 1                            9.28         12.97         11.91         11.31         11.49        11.82       11.29
     Total                            10.56         14.12         13.16         12.51         12.68        13.05       12.49
   Period-end Tier 1 leverage
   ratio                               7.39         10.67         10.11          9.25          9.00         9.54        8.77
   Cash dividends declared to
   net income                         28.38         25.66         24.05         26.05         27.88        27.03       28.01
</TABLE>

                                      -13-
<PAGE>

<TABLE>
<S>                                    <C>       <C>        <C>      <C>       <C>        <C>      <C>
Asset Quality Ratios:
   Allowance for credit losses,
    at period-end, to:
      Total loans, net of unearned        1.59%     1.54%     1.38%     1.37%     1.45%      1.46%      1.38%
       income
      Nonperforming and past-due        222.62    245.72     84.23    548.35    129.66     461.82   1,304.63
       loans
   Annualized net charge-offs to
    average total
      Loans, net of unearned income       0.02      0.12      0.12      0.13      0.12       0.12       0.01
   Nonperforming and past-due
    loans to
      Total loans, net of unearned        0.71      0.63      1.64      0.25      1.11       0.32       0.11
       income
   Nonperforming assets and
    past-due loans
    to total assets, at period-end        1.29      0.49      1.37      1.41      1.66       1.20       0.74
</TABLE>

   _____________________

(a)  Per common share data for 1997, 1996, 1995 and 1994 have been adjusted to
      reflect the two-for-one stock split-up in the form of a 100% stock
      dividend paid in June 1998.

(b)  Net interest margin is the ratio of net interest income, determined on a
      taxable equivalent basis for items exempt from federal tax, to average
      earning assets.


Suburban Bancshares

     Suburban Bancshares' selected historical data is based on its Annual Report
on Form 10-K for the year ended December 31, 1998, its Quarterly Report on Form
10-Q for the quarter ended September 30, 1999 and other financial information
incorporated by reference in and delivered with this proxy statement/prospectus.
You should read this financial information in conjunction with the information
in those Suburban Bancshares reports and other information incorporated by
reference in this proxy statement/prospectus. See "Where You Can Find More
Information" on page 101.

                                      -14-
<PAGE>

                   SUBURBAN BANCSHARES, INC. AND SUBSIDIARY
                     CONDENSED CONSOLIDATED FINANCIAL DATA

<TABLE>
<CAPTION>
                                                                                                             As of or for
                                                                                                           the Nine Months
                                                    As of or for the Year Ended December 31,              Ended September 30,
                                   ----------------------------------------------------------------      ---------------------
                                     1994          1995          1996          1997          1998          1998         1999
                                   --------      --------      --------      --------      --------      --------     --------
                                                                  (dollars in thousands, except per share data)
<S>                                <C>           <C>           <C>           <C>           <C>           <C>          <C>
Consolidated Income Statement:
   Interest income                 $  7,156      $  8,358      $  9,176      $ 11,363      $ 14,246      $ 10,391     $ 10,810
   Interest expense                   2,377         3,119         3,362         4,570         6,337         4,599        4,839
                                   -------------------------------------------------------------------------------------------
   Net interest income                4,779         5,239         5,814         6,793         7,909         5,792       5,971
    Provision (recovery) for
    credit losses                        39          (260)         (227)          254           415           315         369
                                   -------------------------------------------------------------------------------------------
   Net interest income after
    provision for credit losses       4,740         5,499         6,041         6,539         7,494         5,477       5,602
   Noninterest income                   787         1,599           517           774         1,088           722         795
   Noninterest expense                5,308         5,551         5,614         5,511         6,359         4,652       5,330
                                   -------------------------------------------------------------------------------------------
   Income before income taxes           219         1,547           944         1,802         2,223         1,547       1,067
   Income tax expense (benefit)           -             6        (4,058)          671           797           554         357
                                   -------------------------------------------------------------------------------------------
   Net income                      $    219      $  1,541      $  5,002      $  1,131      $  1,426      $    993    $    710
                                   ========      ========      ========      ========      ========      ========    ========
Consolidated Balance Sheet (at
 period-end):
   Assets:
    Cash and cash equivalents      $ 20,810      $ 28,641      $ 20,063      $ 26,328      $ 55,373      $ 66,054    $ 33,033
    Securities, including those      24,073        18,067        21,290        30,360        45,843        34,699      46,444
     available-for-sale
    Loans originated for sale         2,044         3,292         5,933             -         1,814           774         259
    Loans, net of unearned income    64,525        63,022        73,448       113,543       129,885       122,778     136,776
    Allowance for credit losses      (2,750)       (1,467)       (1,508)       (1,473)       (1,524)       (1,452)     (1,646)
    Other assets                      5,527         3,876         6,859         6,908         7,175         6,957       7,936
                                   -------------------------------------------------------------------------------------------
   Total assets                    $114,229      $115,431      $126,085      $175,666      $238,566      $229,810    $222,802
                                   ========      ========      ========      ========      ========      ========    ========

   Liabilities and Equity:
    Deposits                       $104,402      $101,889      $107,573      $152,802      $207,380      $196,132    $187,692
    Short-term borrowings               691             -             -         3,049         9,523        11,627      12,952
    Long-term borrowings                  -             -             -             -             -             -           -
    Other liabilities                   549           446           681           633           951         1,637       1,729
    Stockholders' equity              8,587        13,096        17,831        19,182        20,712        20,414      20,429
                                   -------------------------------------------------------------------------------------------
   Total liabilities and equity    $114,229      $115,431      $126,085      $175,666      $238,566      $229,810    $222,802
                                   ========      ========      ========      ========      ========      ========    ========
Per Share Data:
   Number of shares of Common
    Stock outstanding (in
    thousands)                        9,054        10,951        10,951        10,951        10,951        10,951      11,301
   Net income:
     Basic                         $   0.02      $   0.17      $   0.46      $   0.10      $   0.13      $   0.09    $   0.06
     Diluted                           0.02          0.15          0.44          0.10          0.13          0.09        0.06
   Cash dividends declared:
     Common                               -             -             -             -             -             -           -
     Preferred                            -             -             -             -             -             -           -
   Tangible book value                 0.95          1.20          1.63          1.75          1.89          1.86        1.81
Performance and Capital Ratios:
   Return on average assets            0.21%         1.49%         4.42%         0.76%         0.72%         0.70%       0.44%
   Return on average
    stockholders' equity               2.51         15.29         36.35          6.14          7.14          6.73        4.60
   Net interest margin (a)             5.05          5.50          5.57          5.02          4.33          4.42        4.02
   Average stockholders' equity
    to average total assets            8.31          9.75         12.15         12.42         10.06         10.35        9.63
   Period-end capital to
    period-end risk-weighted
    assets:

     Tier 1                           12.56         16.17         19.19         17.49         15.47         16.06       15.78
     Total                            13.85         17.43         20.45         18.74         16.65         17.27       17.01
   Period-end Tier 1 leverage
   ratio                               8.29         12.21         12.75         10.82          9.13          9.52        9.73
   Cash dividends declared to
   net income                             -             -             -             -             -             -           -
</TABLE>

                                                               -15-
<PAGE>

<TABLE>
<S>                                                   <C>       <C>      <C>        <C>      <C>         <C>        <C>
Asset Quality Ratios:
 Allowance for credit losses, at period-end, to:
   Total loans, net of unearned income                 4.26%     2.33%     2.05%     1.30%     1.17%       1.18%      1.20%
   Nonperforming and past-due loans                   73.92     92.15    187.10     76.60    113.82      101.61     105.51
 Annualized net charge-offs to average total
   loans, net of unearned income                      (0.37)     1.58     (0.36)     0.31      0.30        0.38       0.25
 Nonperforming and past-due loans to
   total loans, net of unearned income                 5.77      2.53      1.10      1.69      1.03        1.16       1.14
 Nonperforming assets and past-due loans
   to total assets, at period-end                      5.90      2.38      0.81      1.29      0.79        0.80       0.91
</TABLE>

 ____________________________

(a)  Net interest margin is the ratio of net interest income, determined on a
     taxable equivalent basis for items exempt from federal tax, to average
     earning assets.


                                      -16-
<PAGE>

Unaudited Pro Forma Condensed Combined Selected Financial Data

     We have included this unaudited pro forma condensed combined summary
information only for the purposes of illustration.  It does not necessarily
indicate what the operating results or financial position of the combined
company would have been if the merger had been completed at the dates indicated.
Moreover, this information does not necessarily indicate what the future
operating results or financial position of the combined company will be.  This
unaudited pro forma condensed combined summary financial information reflects
treatment of the merger as a pooling of interests and does not reflect any
adjustments to conform accounting practices or any cost savings or other
synergies which may result from the merger or any future merger-related
expenses.  The unaudited pro forma balance sheet data gives effect to the merger
as if it had occurred on the date of each balance sheet presented.  The
unaudited pro forma results of operations data gives the effect to the merger as
if it occurred at the beginning of each period presented.

                                      -17-
<PAGE>

                PRO-FORMA CONDENSED CONSOLIDATED FINANCIAL DATA

<TABLE>
<CAPTION>
                                                                                               As of or for
                                                                                              the Nine Months
                                           As of or for the Year Ended December 31,          Ended September 30,
                                           ----------------------------------------          -------------------
                                      1994        1995       1996       1997       1998        1998       1999
                                      ----        ----       ----       ----       ----        ----       ----
                                                   (dollars in thousands, except per share data)
<S>                                  <C>        <C>        <C>        <C>        <C>         <C>        <C>
Consolidated Income Statement (a):
    Interest income                  $ 24,187   $ 30,568   $ 34,998   $ 41,557   $ 47,174    $ 35,099   $ 36,005
    Interest expense                    8,082     11,011     12,131     16,043     19,355      14,305     14,331
                                     ---------------------------------------------------------------------------
    Net interest income                16,105     19,557     22,867     25,514     27,819      20,794     21,674
    Provision for credit losses           281        299        394        917      1,074         832        659
                                     ---------------------------------------------------------------------------
    Net interest income after
      provision for credit losses    $ 15,824     19,258     22,473     24,597     26,745      19,962     21,015
    Noninterest income                  2,291      2,899      2,305      2,956      4,512       3,143      3,364
    Noninterest expense                13,957     15,023     17,695     19,233     21,743      16,107     17,403
                                     ---------------------------------------------------------------------------
    Income before income taxes          4,158      7,134      7,083      8,320      9,514       6,998      6,976
    Income tax expense (benefit)        1,523      2,164     (1,671)     3,021      3,342       2,464      2,399
                                     ---------------------------------------------------------------------------
    Net income                       $  2,635   $  4,970   $  8,754   $  5,299   $  6,172    $  4,534   $  4,577
                                     ========   ========   ========   ========   ========    ========   ========
Consolidated Balance Sheet (at
 period-end):
    Assets:
     Cash and cash equivalents       $ 34,337   $ 56,733   $ 41,294   $ 41,839   $ 87,902    $105,122   $ 57,413
     Securities, including those       62,352     53,408     65,439     97,005    129,859     111,420    156,163
     available-for-sale
     Loans originated for sale          2,504      4,337      7,484      6,557     19,201      12,506      3,253
     Loans, net of unearned income    226,778    253,713    311,323    378,737    404,298     390,993    442,115
     Allowance for credit losses       (5,328)    (4,396)    (4,801)    (5,105)    (5,489)     (5,359)    (5,873)
     Other assets                      17,794     14,661     22,580     30,084     30,130      30,217     29,818
                                     ---------------------------------------------------------------------------
    Total assets                     $338,437   $378,456   $443,319   $549,117   $665,901    $644,899   $682,889
                                     ========   ========   ========   ========   ========    ========   ========

    Liabilities and Equity:
     Deposits                        $293,865   $320,051   $362,213   $466,159   $546,716    $526,804   $541,716
     Short-term borrowings             17,587     15,299     30,127     26,774     36,535      40,715     56,612
     Long-term borrowings                   -          -          -          -     20,000      15,000     20,000
     Other liabilities                  1,525      1,946      2,173      2,617      3,584       4,216      4,221
     Stockholders' equity              25,460     41,160     48,806     53,567     59,066      58,164     60,340
                                     ---------------------------------------------------------------------------
    Total liabilities and equity     $338,437   $378,456   $443,319   $549,117   $665,901    $644,899   $682,889
                                     ========   ========   ========   ========   ========    ========   ========
Per Share Data (b):
    Number of shares of Common Stock
     outstanding (in thousands)
      Conversion factor - .2338         4,197      6,852      6,856      6,961      7,122       7,133      7,148
      Conversion factor - .2196         4,069      6,696      6,701      6,805      6,967       6,977      6,988
    Net income (c):
     Basic
      Conversion factor - .2338      $   0.57   $   0.94   $   1.28   $   0.77   $   0.87    $   0.64   $   0.64
      Conversion factor - .2196          0.59       0.96       1.31       0.79       0.89        0.66       0.65
     Diluted
      Conversion factor - .2338          0.47       0.80       1.22       0.73       0.85        0.62       0.63
      Conversion factor - .2196          0.48       0.82       1.25       0.75       0.87        0.64       0.65
    Cash dividends declared (d):
     Common
      Conversion factor - .2338          0.04       0.06       0.13       0.16       0.19        0.13       0.15
      Conversion factor - .2196          0.04       0.06       0.13       0.16       0.19        0.14       0.15
     Preferred                           1.20       1.30          -          -          -           -          -
    Tangible book value (e):
      Conversion factor - .2338          6.07       6.01       7.12       7.70       8.29        8.15       8.44
      Conversion factor - .2196          6.26       6.15       7.28       7.87       8.48        8.34       8.64
</TABLE>

                                     -18-
<PAGE>

<TABLE>
<S>                                              <C>         <C>        <C>        <C>        <C>           <C>        <C>
Performance and Capital Ratios:
    Return on average assets                      0.83%       1.44%      2.22%      1.07%      1.03%         1.03%      0.93%
    Return on average stockholders' equity       10.61       15.51      20.23      10.38      10.90         10.84      10.25
    Net interest margin (f)                       5.62        6.17       6.31       5.65       5.04          5.18       4.78
    Average stockholders' equity to
      average total assets                        7.79        9.28      10.99      10.33       9.41          9.54       9.08
    Period-end capital to period-end
      risk-weighted assets:
      Tier 1                                     10.22%      13.85%     13.66%     12.86%     12.61%        12.98%     12.53%
      Total                                      11.51       15.02      14.91      14.07      13.79         14.21      13.73
    Period-end Tier 1 leverage ratio              7.69       11.11      10.87       9.73       9.04          9.53       9.08
    Cash dividends declared to net income         5.58        8.57      10.32      20.49      21.44         21.11      23.66
</TABLE>


    ________________________

 (a)      This unaudited pro-forma condensed consolidated income statement data
          does not consider charges or credits which will result directly from
          the transaction and which will be included in the income of the
          combined entity within the 12 months succeeding the transaction. It is
          anticipated that, as a result of the merger, the combined entity will
          incur approximately $______ in merger related expenses for items such
          as legal, investment advisory, accounting, and severance pay. These
          charges will be offset by approximately $____ for the related tax
          effect at Columbia Bancorp's effective tax rate of 34%.
 (b)      Per common share data for 1997, 1996, 1995 and 1994 have been adjusted
          to reflect the two-for-one stock split-up in the form of a 100% stock
          dividend paid by Columbia Bancorp in June 1998.
 (c)      Pro-forma earnings per common share, basic and diluted, represents
          historical net income divided by the number of shares of Columbia
          Bancorp common stock which will be issued and outstanding following
          completion of the Merger based on the appropriate conversion factor
          and including the effects of dilutive securities in the case of
          diluted pro-forma income per common share.

 (d)      Pro-forma cash dividends per share is calculated by dividing the
          historical amount of dividends declared by Columbia Bancorp (no
          dividends were declared by Suburban Bancshares during the periods
          presented) by the sum of (1) the total number of shares of Columbia
          Bancorp common stock outstanding at such date and (2) the total number
          of shares of Suburban Bancshares common stock outstanding at such date
          multiplied by the appropriate conversion factor.
 (e)      Pro-forma tangible book value per share is calculated by dividing
          total pro-forma combined stockholders' equity as of the applicable
          date by the sum of (1) the total number of shares of Columbia Bancorp
          common stock outstanding at such date and (2) the total number of
          shares of Suburban Bancshares common stock outstanding at such date
          multiplied by the appropriate conversion factor.
 (f)      Net interest margin is the ratio of net interest income, determined on
          a taxable equivalent basis for items exempt from federal tax, to
          average earning assets.


                                      -19-
<PAGE>

Comparative Per Share Data


     The following table sets forth certain historical and unaudited pro forma
per share data of Columbia Bancorp and Suburban Bancshares as well as equivalent
per share data with respect to one share of Suburban Bancshares common stock on
a pro forma basis for the merger.  You should read the data presented below in
conjunction with the unaudited pro forma combined condensed financial data, and
related notes, and historical financial statements, and related notes, of
Columbia Bancorp and Suburban Bancshares which are incorporated by reference in
this document or included elsewhere in this document.  See "Where You Can Find
More Information."

                                      -20-
<PAGE>

<TABLE>
<CAPTION>
                                                                                         As of or for the
                                                      As of or for the Year Ended        Nine Months Ended
                                                              December 31,                 September 30,
                                                      ----------------------------     ---------------------
                                                        1996      1997      1998         1998        1999
                                                      --------  --------  --------     --------    ---------
<S>                                           <C>     <C>       <C>       <C>          <C>         <C>
Columbia Bancorp
   Basic earnings per share
       Historical                                     $   0.87  $   0.96  $   1.05     $   0.78    $    0.86
       Pro-forma combined (a)
                     Conversion factor        0.2338      1.28      0.77      0.87         0.64         0.64
                     Conversion factor        0.2196      1.31      0.79      0.89         0.66         0.65
   Diluted earnings per share
       Historical                                         0.83      0.91      1.03         0.77         0.84
       Pro-forma combined (a)
                     Conversion factor        0.2338      1.22      0.73      0.85         0.62         0.63
                     Conversion factor        0.2196      1.25      0.75      0.87         0.64         0.65
   Cash dividends declared per share
       Historical                                         0.21      0.25      0.29         0.21         0.24
       Pro-forma combined (b )
                     Conversion factor        0.2338      0.13      0.16      0.19         0.13         0.15
                     Conversion factor        0.2196      0.13      0.16      0.19         0.14         0.15
   Tangible book value per share
       Historical                                         7.15      7.77      8.39         8.23         8.85
       Pro-forma combined (c )
                     Conversion factor        0.2338      7.12      7.70      8.29         8.15         8.44
                     Conversion factor        0.2196      7.28      7.87      8.48         8.34         8.64

 Suburban Bancshares
   Basic earnings per share
       Historical                                     $   0.46  $   0.10  $   0.13     $   0.09    $    0.06
       Pro-forma equivalent (a)
                     Conversion factor        0.2338      0.30      0.18      0.20         0.15         0.15
                     Conversion factor        0.2196      0.29      0.17      0.20         0.14         0.14
   Diluted earnings per share
       Historical                                         0.44      0.10      0.13         0.09         0.06
       Pro-forma equivalent (a)
                     Conversion factor        0.2338      0.29      0.17      0.20         0.15         0.15
                     Conversion factor        0.2196      0.27      0.16      0.19         0.14         0.14
   Dividends declared per share
       Historical                                            -         -         -            -            -
       Pro-forma equivalent (b)
                     Conversion factor        0.2338      0.03      0.04      0.04         0.03         0.04
                     Conversion factor        0.2196      0.03      0.04      0.04         0.03         0.03
   Tangible book value per share
       Historical                                         1.63      1.75      1.89         1.86         1.81
       Pro-forma equivalent (c )
                     Conversion factor        0.2338      1.66      1.80      1.94         1.91         1.97
                     Conversion factor        0.2196      1.60      1.73      1.86         1.83         1.90
</TABLE>

                                      -21-
<PAGE>

(a)  Columbia Bancorp pro-forma earnings per common share, basic and diluted,
     represents historical net income for Columbia Bancorp and Suburban combined
     on the assumption that Columbia Bancorp and Suburban had been combined for
     the periods presented on a pooling of interests basis, divided by the
     number of shares of Columbia Bancorp common stock which will be issued and
     outstanding following completion of the Merger based on the appropriate
     conversion factor and including the effects of dilutive securities in the
     case of diluted pro-forma income per common share. Suburban equivalent pro-
     forma earnings per common share, basic and diluted, represents Columbia
     Bancorp pro-forma earnings per common share multiplied by the appropriate
     conversion factor.






(b)  Pro-forma cash dividends per share of Columbia Bancorp common stock is
     calculated by dividing the historical amount of dividends declared by
     Columbia Bancorp (no dividends were declared by Suburban during the periods
     presented) by the sum of (1) the total number of shares of Columbia Bancorp
     common stock outstanding at such date and (2) the total number of shares of
     Suburban common stock outstanding at such date multiplied by the
     appropriate conversion factor. Pro-forma equivalent dividends per share of
     Suburban common stock represents the pro-forma dividend declared per share
     of Columbia Bancorp common stock multiplied by the appropriate conversion
     factor.






(c ) Pro-forma tangible book value per share of Columbia Bancorp common stock is
     calculated by dividing total pro forma combined stockholders' equity as of
     the applicable date by the sum of (1) the total number of shares of
     Columbia Bancorp common stock outstanding at such date and (2) the total
     number of shares of Suburban common stock outstanding at such date
     multiplied by the appropriate conversion factor. Equivalent pro-forma book
     value per share of Suburban common stock represents the pro-forma book
     value per share of Columbia Bancorp common stock multiplied by the
     appropriate conversion factor.


                                      -22-
<PAGE>

                          FORWARD-LOOKING STATEMENTS

     This proxy statement/prospectus contains and incorporates by reference
statements that constitute "forward-looking statements" within the meaning of
the Private Securities Litigation Reform Act of 1995. These statements relate,
among other things, to information or assumptions about earnings per share,
capital and other expenditures, dividends, financing plans, capital structure,
cash flows, future economic performance, operating income improvements, cost
savings and management's plans, goals and objectives for future operations.
These forward-looking statements generally may be identified by their reference
to a future period or periods or by the use of forward-looking terminology such
as "may," "will," "intend," "should," "expect," "anticipate," "believe,"
"estimate," "continue," the negatives of those terms or similar expressions.
You should understand that forward-looking statements are estimates reflecting
the judgment of management of Columbia Bancorp and Suburban Bancshares, not
guarantees of future performance.  Such statements are subject to risks,
uncertainties and assumptions, including, but not limited to:

     .    combining the businesses of Columbia Bancorp and Suburban Bancshares
          may cost more than we expect;

     .    integrating the businesses of Columbia Bancorp and Suburban Bancshares
          and retaining key personnel may be more difficult than we expect;

     .    our revenues after the merger may be lower than we expect, or our
          operating costs may be higher than we expect;

     .    expected cost savings from the merger may not be fully realized or may
          not be realized within the expected time frame;

     .    growth in business and/or customers after the merger may be different
          than we expect;

     .    there may be increases in competitive pressure among financial
          institutions;

     .    changes in the interest rate environment may reduce interest margins;

     .    general economic conditions, either nationally or in the region in
          which the combined company will be doing business, or conditions in
          securities markets, may be less favorable than we currently
          anticipate;

     .    legislation or regulatory changes may adversely affect our business;

     .    technological changes, including "Year 2000" data system compliance
          issues, may be more difficult or expensive than anticipated; or

     .    other risks and uncertainties described in "Risk Factors" or in the
          other SEC filings of Columbia Bancorp and Suburban Bancshares.

     Should one or more of these risks or uncertainties affect the business of
Columbia Bancorp and Suburban Bancshares or should underlying assumptions prove
incorrect, actual results, performance or

                                      -23-
<PAGE>

achievements in 2000 and beyond could differ materially from those expressed in,
or implied by, such forward-looking statements.

                                      -24-
<PAGE>

                                 RISK FACTORS

     In addition to the other information provided or incorporated by reference
in this proxy statement/prospectus, you should consider the following factors
carefully in evaluating whether to vote in favor of the merger. You should also
refer to "Forward-Looking Statements" on page 22.

Risks Related to the Merger

     Columbia Bancorp may not successfully integrate and manage the operations
of Suburban Bancshares which could adversely effect  future earnings.  Columbia
Bancorp has agreed to acquire Suburban Bancshares and its wholly-owned
subsidiary Suburban Bank.  Suburban Bancshares has an operating history, but not
under Columbia Bancorp's management.  Columbia Bank, the surviving banking
entity, will hold substantially all of the assets and conduct substantially all
of the business of Columbia Bancorp.  If Columbia Bancorp cannot manage the
combined bank successfully, it will reduce the operating results of Columbia
Bancorp. The risks of this acquisition include the following:

     .    management will have to divert time to integrate the businesses;

     .    Suburban Bancshares may have unexpected problems or risks in
          operations, personnel, technology or credit;

     .    Columbia Bancorp may lose the customers and employees of Suburban
          Bancshares;

     .    new management may not work smoothly with employees and customers;

     .    the assimilation of new operations, sites and personnel could divert
          resources from regular banking operations; and

     .    Columbia Bancorp may have trouble instituting and maintaining uniform
          standards, controls, procedures and policies.

     Columbia Bancorp may not realize anticipated operating efficiencies, which
could hurt Columbia Bancorp's profitability. Columbia Bancorp's business plan
calls for Columbia Bancorp to increase profits by reducing costs, expanding
services and integrating administrative functions. Columbia Bancorp may not
realize these operating efficiencies, or may not realize them as soon as
anticipated. If Columbia Bancorp does not realize operating efficiencies as
anticipated, it could hurt profitability.

                                      -25-
<PAGE>

     Unanticipated costs relating to the merger could reduce Columbia Bancorp's
future earnings per share.  We believe that we have reasonably estimated the
likely costs of integrating the operations of Columbia Bancorp and Suburban
Bancshares, and the incremental costs of operating as a combined company.
However, it is possible that unexpected transaction costs such as taxes, fees or
professional expenses or unexpected future operating expenses such as increased
personnel costs or increased taxes, as well as other types of unanticipated
adverse developments, could have a material adverse effect on our results of
operations and financial condition. If unexpected costs are incurred, the merger
could adversely affect Columbia Bancorp's earnings per share. In other words, if
the merger is completed, it is possible that the earnings per share of Columbia
Bancorp common stock could be less than they would have been if the merger had
not been completed.

     You may incur federal income tax on shares received in the merger if the
merger does not qualify as a tax-free reorganization.  We have structured the
merger to qualify as a tax-free reorganization under Section 368(a) of the
Internal Revenue Code of 1986. Although the Internal Revenue Service has not
provided a ruling on the matter, we will obtain a legal opinion  that the merger
qualifies as tax-free. This opinion neither binds the IRS nor prevents the IRS
from adopting a contrary position. If the merger fails to qualify as a tax-free
reorganization, as a Suburban Bancshares stockholder, you would recognize gain
or loss on each share of Suburban Bancshares common stock surrendered in the
amount of the difference between your basis in such share and the fair market
value of the shares of Columbia Bancorp and cash for any fractional shares you
receive in exchange for it at the time of the merger.


Risks Related to the Combined Companies

     Failure to address year 2000 problems could impair operations and following
the merger could subject Columbia Bancorp to liability from its customers and
others.  Columbia Bancorp and Suburban Bancshares, like all financial
institutions, face challenges posed by the century date change.  Each
institution has taken the steps to make its own information and environmental
systems Year 2000 compliant, in accordance with regulatory requirements.
Preparations have included development of contingency plans to reduce the impact
of any failures which may occur.  For more information on the specific steps
that we are taking, please refer to "Management's Discussion and Analysis of
Financial Condition and Results of Operations of Suburban Bancshares--Year 2000
Compliance" which is incorporated herein by reference to Suburban Bancshares'
Quarterly Report on Form 10-Q for the quarter ended September 30, 1999 which is
delivered with this proxy statement/prospectus, "Management's Discussion and
Analysis of Financial Condition and Results of Operations of Columbia Bancorp--
Year 2000 Readiness Disclosure" which is incorporated herein by reference to
Columbia Bancorp's Annual Report on Form 10-K for the fiscal year ended December
31, 1998 which is delivered with this proxy statement/prospectus and
"Management's' Discussion and Analysis of Financial Condition and Results of
Operations of Columbia Bancorp - Year 2000 Readiness Disclosure" which is
incorporated herein by reference to Columbia Bancorp's quarterly report on Form
10-Q for the quarter ended September 30, 1999 and delivered with this proxy
statement/prospectus.

     If Columbia Bancorp loses key employees subsequent to the merger Columbia
Bancorp's business may suffer.  Following the merger, if Columbia Bancorp lost
key employees temporarily or permanently, it could hurt Columbia Bancorp's
business.  Columbia Bancorp could be particularly hurt if Columbia Bancorp's key
employees went to work for competitors. Columbia Bancorp's future success
depends on the continued contributions of its existing senior management
personnel, some of whom have agreements with Columbia Bancorp which include
provisions that limit their ability to compete against

                                      -26-
<PAGE>

Columbia Bancorp at another company. Columbia Bancorp does not maintain key-
person life insurance on any of its personnel. However, in order to partially
offset the costs associated with its deferred compensation plan, Columbia Bank
has purchased life insurance contracts on the lives of the senior executive
officers who participate in the plan, with Columbia Bank as the beneficiary.

     Following the merger, deterioration of economic conditions in the
Baltimore/Washington metropolitan area could adversely affect Columbia Bancorp's
loan portfolio and reduce the demand for our services.  Both Columbia Bancorp
and Suburban Bancshares focus their business in the Baltimore/Washington
metropolitan area. An economic slow-down in the Baltimore/Washington
metropolitan area could have the following consequences, any of which could
reduce Columbia Bancorp's net income subsequent to the merger:

     .    loan delinquencies may increase;

     .    problem assets and foreclosures may increase;

     .    claims and lawsuits may increase;

     .    demand for the banks' products and services may decline; and

     .    collateral for loans made by the banks, especially real estate, may
          decline in value, in turn reducing customers' borrowing power,
          reducing the value of assets associated with problem loans and
          reducing collateral coverage of the banks' existing loans.

     Changes in interest rates could reduce Columbia Bancorp's income and cash
flows subsequent to the merger.  Columbia Bancorp's and Suburban Bancshares'
income and cash flows depend to a great extent on "interest rate differentials"
and the resulting net interest margins, i.e., the difference between the
interest rates earned on interest-earning assets such as loans and investment
securities, and the interest rates paid on interest-bearing liabilities such as
deposits and borrowings. These rates are highly sensitive to many factors which
are beyond our control, including general economic conditions and the policies
of various governmental and regulatory agencies, in particular, the Federal
Reserve Board. Changes in monetary policy, including changes in interest rates,
will influence the origination of loans, the purchase of investments, the
generation of deposits, and the rates received on loans and investment
securities and paid on deposits. Fluctuations in these areas may adversely
affect Columbia Bancorp subsequent to the merger.

     A downturn in the real estate market could seriously impair Columbia
Bancorp's loan portfolio subsequent to the merger.  As of September 30, 1999,
approximately 81% of Columbia Bank's loan portfolio and 51% of Suburban Bank's
loan portfolio (approximately 72% on a pro forma basis) consisted of loans
secured by various types of real estate primarily located in the
Baltimore/Washington metropolitan area.  A more specific breakdown as of
September 30, 1999 is as follows:

                                      -27-
<PAGE>

<TABLE>
<CAPTION>
                                            Columbia Bank       Suburban Bank      Pro Forma
                                           ---------------     ---------------     -----------
<S>                                        <C>                 <C>                 <C>
Construction and development:
     Residential                                  28.2%               2.4%             20.2%
     Commercial                                    2.7                2.2               2.6
Consumer loans secured by residential
 real estate                                      37.9                8.2              28.7
Commercial properties                             12.9               37.9              20.7
Other                                              0.1                  -                 -
                                           ---------------------------------------------------
                                                  81.1%              50.7%             72.2%
</TABLE>

     If real estate values decline significantly, especially in the
Baltimore/Washington metropolitan area, the collateral for these loans will
provide less security and Columbia Bancorp may suffer losses on defaulted loans.

     Environmental laws could force Columbia Bancorp to pay for environmental
problems subsequent to the merger.  The cost of cleaning up or paying damages
and penalties associated with environmental problems could increase Columbia
Bancorp's operating expenses subsequent to the merger. If a borrower defaults on
a loan secured by real property, a bank may purchase the property in foreclosure
or accept a deed to the property surrendered by the borrower. We may also take
over the management of commercial properties whose owners have defaulted on
loans. We also own and lease premises where our branches and other facilities
are located. While Columbia Bancorp and Suburban Bancshares each have lending,
foreclosure and facilities guidelines intended to exclude properties with an
unreasonable risk of contamination, hazardous substances may exist on some of
the properties that we own, manage or occupy. We face the risk that
environmental laws could force us to clean the properties at our expense.

     Columbia Bancorp's credit loss reserves may not cover actual loan losses
subsequent to the merger.  If the actual credit losses exceed the amount
reserved, it will hurt Columbia Bancorp's business subsequent to the merger.
Columbia Bancorp and Suburban Bancshares attempt to limit the risk that
borrowers will fail to repay loans by carefully underwriting the loans. Losses
nevertheless occur. Columbia Bancorp and Suburban Bancshares creates reserves
for estimated credit losses in their accounting records. We base these
allowances on estimates of the following:

     .    industry standards;

     .    historical experience with our loans;

     .    evaluation of current economic conditions;

     .    regular reviews of the quality mix and size of the overall loan
          portfolio;

     .    regular reviews of delinquencies; and

     .    the quality of the collateral underlying the loans.

     An increase in non-performing assets would reduce Columbia Bancorp's
income and increase expenses subsequent to the merger. If the level of non-
performing assets rises in the future, it could adversely affect Columbia
Bancorp's operating results subsequent to the merger. Non-performing

                                      -28-
<PAGE>

assets include real estate that has been acquired through foreclosure of unpaid
loans, loans on which the borrowers are not making their required payments and
loans that have been restructured to permit the borrower to have smaller
payments. To the extent that assets are non-performing, the bank will have less
cash available for lending and other activities.

     Governmental regulation may impair our operations or restrict our growth.
If Columbia Bancorp or Suburban Bancshares fails to comply with the federal and
state bank regulations, subsequent to the merger the regulators may limit the
activities or growth, fine Columbia Bancorp or ultimately put Columbia Bancorp
out of business. Banking laws and regulations change from time to time. Bank
regulation can hinder Columbia Bancorp's ability to compete with financial
services companies that are not regulated or are less regulated. In addition,
bank regulators impose material compliance costs on us.

     Federal and state bank regulatory agencies regulate many aspects of
Columbia Bancorp's and Suburban Bancshares' operations. These areas include:

     .    the capital we must maintain;

     .    the kinds of activities we can do;

     .    the kinds and amounts of investments we can make;

     .    the locations of our offices;

     .    insurance of our deposits and the premiums we must pay for this
          insurance; and

     .    how much cash we must set aside as reserves for deposits.


     Provisions in Columbia Bancorp's charter documents and agreements will
delay or prevent changes in control of our corporation or our management. These
provisions make it more difficult for another company to acquire Columbia
Bancorp, which could reduce the market price of Columbia Bancorp's common stock
and the price that you will receive if you sell your shares of Columbia Bancorp
common stock in the future. These provisions include the following:

     .    a provision requiring that 80% of the stockholders approve a vote when
          stockholders approve certain amendments to the charter and bylaws;

     .    a requirement that stockholders give advance notice of matters to be
          raised at a meeting of stockholders; and

     .    staggered terms of office for members of the board of directors.

     Columbia Bancorp also has contractual arrangements that impede changes in
control, including severance agreements for our senior officers and commitments
to issue options.

     Columbia Bancorp's acquisition strategy could be dilutive to its
stockholders or adversely affect its profitability. Columbia Bancorp has grown
through acquisitions in past years and anticipates

                                      -29-
<PAGE>

that it will make additional acquisitions in the future. Columbia Bancorp
evaluates strategic opportunities not only in the banking industry but also in
related financial service industries. One or more future acquisitions could be
material to Columbia Bancorp. Columbia Bancorp may need to issue more common
stock to pay for those acquisitions, which would further dilute the percentage
ownership interest of all its stockholders at the time of the acquisition and
could dilute earnings or book value per share. Acquisitions also could require
Columbia Bancorp to use substantial cash or other liquid assets or to incur
debt. In those events, Columbia Bancorp could become more susceptible to
economic downturns and competitive pressures.

     The banking industry is highly competitive and Columbia Bancorp cannot
assure you that it will be able to compete effectively subsequent to the merger.
Columbia Bancorp and Suburban Bancshares operate in a competitive environment
and compete for deposits and loans with commercial banks, thrift institutions
and other financial institutions that may have greater financial resources than
those available to Columbia Bancorp subsequent to the merger. These institutions
may have substantially higher lending limits than Columbia Bancorp and Suburban
Bancshares and may provide certain additional services for their customers, such
as trust and investment services, which Columbia Bancorp and Suburban Bancshares
do not currently offer directly to their customers. Columbia Bancorp and
Suburban Bancshares also compete for deposits with money market mutual funds.

                                      -30-
<PAGE>

                    GENERAL INFORMATION ABOUT THE MEETINGS

Date, Time and Place of the Meetings

     The meeting of the Columbia Bancorp stockholders will be held at __:____
__.m., local time, on _____________________, 1999, at
____________________________________.

     The meeting of the Suburban Bancshares stockholders will be held on
____________________,1999 at __:__ _.m., local time, at
________________________________________________________.

Record Date and Outstanding Shares

     The Columbia Bancorp board of directors has fixed the close of business on
__________________, 1999 as the record date for the determination of the holders
of Columbia Bancorp common stock entitled to receive notice of and to vote at
the Columbia Bancorp meeting. Only stockholders of record on the record date are
entitled to receive notice of and to vote at the Columbia Bancorp meeting or any
adjournments or postponement of the meetings. As of the Columbia Bancorp record
date, there were_______________________ shares of Columbia Bancorp common stock
issued and outstanding and held by approximately _________ holders of record.
Each holder of shares of Columbia Bancorp common stock is entitled to one vote
per share held of record on the record date.

     The Suburban Bancshares board of directors has fixed the close of business
on _________________, 1999, as the record date for the determination of the
holders of Suburban Bancshares common stock entitled to receive notice of and to
vote at the Suburban Bancshares meeting or any adjournments or postponement of
the meeting. Only stockholders of record on the record date will be entitled to
receive notice of and to vote at the Suburban Bancshares meeting. As of the
Suburban Bancshares record date, there were ________________ shares of Suburban
Bancshares common stock issued and  outstanding and held by approximately
_________ holders of record.  Each holder of shares of Suburban Bancshares
common stock is entitled to one vote per share held of record on the record
date.

Purpose of the Meetings

     Columbia Bancorp.  Columbia Bancorp is furnishing this proxy
statement/prospectus to its stockholders in connection with the solicitation of
proxies by Columbia Bancorp's board of directors for use at the Columbia Bancorp
meeting.  The purpose of the meeting is to consider and vote upon the proposal
to approve and adopt the merger agreement and to transact such other business as
may properly come before the meeting or any adjournments or postponements
thereof. Pursuant to the merger agreement, at the effective time, the former
stockholders of Suburban Bancshares will receive shares of Columbia Bancorp
common stock for their shares of Suburban Bancshares common stock.  Stockholders
of Suburban Bancshares will receive shares of Columbia Bancorp common stock
equivalent to an average market value of $3.00 per share.  The conversion ratio
necessary to cause the average market value of shares of Columbia Bancorp common
stock exchanged for each share of Suburban Bancshares common stock to be $3.00
per share will continually change until the merger is completed, except that the
conversion ratio will not be above 0.2338 nor below 0.2196.

                                      -31-
<PAGE>

     No fractional shares will be issued.  Instead, stockholders will be paid in
cash the amount equal to the fractional share multiplied by the closing price of
one share of Columbia Bancorp common stock on the date the merger is completed.

     In unanimously approving the merger agreement and the transactions
contemplated in connection with the merger, the members of the Columbia Bancorp
board of directors have determined that the merger is advisable and in the best
interests of the Columbia Bancorp stockholders and recommend that the Columbia
Bancorp stockholders vote in favor of the approval and adoption of the merger
agreement and the merger.

     Suburban Bancshares.  Suburban Bancshares is furnishing this proxy
statement/prospectus to its stockholders in connection with the solicitation of
proxies by Suburban Bancshares' board of directors for use at the Suburban
Bancshares meeting. The purpose of the meeting is to consider and vote upon the
proposal to approve and adopt the merger agreement and to transact such other
business as may properly come before the meeting or any adjournments or
postponements thereof. Pursuant to the merger agreement, at the effective time,
the former stockholders of Suburban Bancshares will receive shares of Columbia
Bancorp common stock equivalent to an average market value of $3.00 per share.
The conversion ratio necessary to cause the average market value of shares of
Columbia Bancorp common stock exchanged for each share of Suburban Bancshares
common stock to be $3.00 per share will continually change until the merger is
completed, except that the conversion ratio will not be above 0.2338 nor below
0.2196.

     No fractional shares will be issued.  Instead, stockholders will be paid in
cash the amount equal to the fractional share multiplied by the average daily
high and low trade prices per share of Columbia Bancorp common stock for the 10
trading days ending three trading days before the effective date.

     In unanimously approving the merger agreement and the transactions
contemplated in connection with the merger, the members of the Suburban
Bancshares board of directors have determined that the merger is advisable and
in the best interests of the Suburban Bancshares stockholders and recommend that
the Suburban Bancshares stockholders vote in favor of the approval and adoption
of the merger agreement and the merger.

Vote Required

     Columbia Bancorp.  Each share of Columbia Bancorp common stock is entitled
to one vote per share with respect to the merger agreement and other matters
properly submitted at the Columbia Bancorp meeting.  Assuming that a quorum is
present at the Columbia Bancorp meeting, (1) approval and adoption of the merger
agreement and the merger requires the affirmative vote, in person or by proxy,
of two-thirds of the outstanding shares of Columbia Bancorp common stock  and
(2) approval and adoption of other matters that come before the meeting
generally requires the affirmative vote, in person or by proxy, of a majority of
the votes cast on the matter at the Columbia Bancorp meeting. Stockholder
approval of the merger agreement is required under Maryland law, and such
approval is a condition to the merger.

     Columbia Bancorp stockholders do not have dissenters' rights of appraisal
with respect to the issuance of shares of Columbia Bancorp common stock in the
merger.

                                      -32-
<PAGE>

     The presence at the Columbia Bancorp meeting, either in person or by proxy,
of the holders of a majority of the votes entitled to vote at the meeting
constitutes a quorum for the transaction of business. For purposes of
determining whether there is a quorum at the Columbia Bancorp meeting,
abstentions and broker non-votes will be treated as shares that are present.

     Under the rules of The Nasdaq Stock Market, brokers who hold shares in
street name for customers will not have the authority to vote on the proposed
merger unless they receive specific instructions from the beneficial owners.
Accordingly, the failure to provide brokers with specific instructions to vote
for the merger will have the same effect as a vote against the merger. As
required by Maryland law, abstentions and broker non-votes will not be counted
in determining whether Columbia Bancorp stockholders have approved the other
proposals.

     All directors and executive officers of Columbia Bancorp have executed a
support agreement to vote all of the shares of Columbia Bancorp common stock
which they beneficially own in favor of the merger.  As of September 30, 1999,
directors and executive officers of Columbia Bancorp and their affiliates
beneficially owned and were entitled to vote 979,698 shares of Columbia Bancorp
common stock, which represented 21.7% of the 4,506,035 shares of the Columbia
Bancorp common stock outstanding.

     Suburban Bancshares.  Each share of Suburban Bancshares common stock is
entitled to one vote per share with respect to the merger agreement and other
matters properly submitted at the Suburban Bancshares meeting. Assuming that a
quorum is present at the Suburban Bancshares meeting, (1) approval and adoption
of the merger agreement and the merger requires the affirmative vote, in person
or by proxy, of a majority of the outstanding shares of Suburban Bancshares
common stock entitled to vote at the Suburban Bancshares meeting and (2)
approval and adoption of other matters that come before the meeting requires the
affirmative vote, in person or by proxy, of a majority of the votes cast on the
matter. Stockholder approval of the merger agreement is required under Delaware
law, and such approval is a condition to the merger.

     If the merger is completed, Suburban Bancshares stockholders who do not
vote for the adoption of the merger agreement and who otherwise comply with
Section 262 of the Delaware General Corporation Law will be entitled to
appraisal rights under Delaware law.  We have attached a copy of Section 262 as
Appendix H.

     The presence at the Suburban Bancshares meeting, in person or by properly
executed proxy, of the holders of a majority of the shares of Suburban
Bancshares common stock outstanding and entitled to vote at the Suburban
Bancshares meeting is necessary to constitute a quorum for the transaction of
business. For purposes of determining whether there is a quorum at the Suburban
Bancshares meeting, abstentions and broker non-votes will be treated as shares
that are present.

     Under the rules of The Nasdaq Stock Market, brokers who hold shares in
street name for customers will not have the authority to vote on the proposed
merger unless they receive specific instructions from the beneficial owners.
Accordingly, the failure to provide brokers with specific instructions to vote
for the merger will have the same effect as votes against the merger. As
required under Delaware law, abstentions and broker non-votes will not be
counted in determining whether Suburban Bancshares stockholders have approved
the other proposals.

     All directors and executive officers of Suburban Bancshares have executed a
support agreement to vote all of the shares of Suburban Bancshares common stock
which they beneficially own in favor of

                                      -33-
<PAGE>

the merger. As of September 30, 1999, directors and executive officers of
Suburban Bancshares and their affiliates beneficially owned and were entitled to
vote 2,263,091 shares of Suburban Bancshares common stock, which represented
20.0% of the 11,301,218 shares of the Suburban Bancshares common stock
outstanding.

Voting of Proxies

     Columbia Bancorp.  If the accompanying proxy card is properly signed and
returned to Columbia Bancorp and not revoked before a vote is taken at the
Columbia Bancorp meeting, it will be voted in accordance with the instructions
indicated on the proxy card. If the proxy card is signed and returned without
indicating any voting directions, the proxy will be voted FOR approval and
adoption.  Brokers who hold shares in street name for customers do not have
authority to vote on the proposed merger unless they receive specific
instructions from the beneficial owners.  If you hold your shares in street
name, please see the voting form provided by your broker for additional
information regarding the voting of your shares.

     Columbia Bancorp is not aware of any business to be acted on at the
Columbia Bancorp meeting, except as described in this proxy
statement/prospectus. If any other matters are properly presented to the
Columbia Bancorp meeting, or any adjournments or postponements of the meeting,
the persons appointed as proxies or their substitutes will have discretion to
vote or act on the matter according to their best judgment and applicable law
unless the proxy indicates otherwise.

     Suburban Bancshares.  If the accompanying proxy card is properly signed and
returned to Suburban Bancshares and not revoked before a vote is taken at the
Suburban Bancshares meeting, it will be voted in accordance with instructions
indicated on the proxy card. If a proxy card is signed and returned without
indicating any voting instructions, shares of Suburban Bancshares common stock,
represented by the proxy will be voted FOR approval and adoption of the merger
agreement and the merger. Brokers who hold shares in street name for customers
do not have authority to vote on the proposed merger unless they receive
specific instructions from the beneficial owners.  If you hold your shares in
street name, please see the voting form provided by your broker for additional
information regarding the voting of your shares.

     Suburban Bancshares is not aware of any business to be acted upon at the
Suburban Bancshares meeting, except as described in this proxy
statement/prospectus. If any other matters are properly presented to the
Suburban Bancshares meeting, or any adjournments or postponements of the
meeting, the persons appointed as proxies or their substitutes will have
discretion to vote or act on the matter according to their best judgment and
applicable law unless the proxy indicates otherwise.

Authorization to Vote on Adjournment and Other Matters

     Columbia Bancorp.  By signing the proxy, a Columbia Bancorp stockholder
authorizes the proxy holder to vote in his discretion regarding any procedural
motions which may come before the Columbia Bancorp meeting. For example, this
authority could be used to adjourn the meeting if Columbia Bancorp believes it
is desirable to do so. Adjournment or other procedural matters could be used to
obtain more time before a stockholder vote in order to solicit additional
proxies or to provide additional information to Columbia Bancorp stockholders.
To the extent a Columbia Bancorp stockholder intends to vote against the merger
agreement, such stockholder would have no incentive to vote in favor of

                                      -34-
<PAGE>

discretionary adjournment by the Columbia Bancorp board of directors, which
would allow Columbia Bancorp to adjourn the meeting in order to solicit
additional votes in favor of the merger agreement. Columbia Bancorp has no plans
to adjourn the meeting at this time, but it intends to attempt to do so if it
believes that doing so would promote stockholder interests.

     The failure to return a proxy or to vote in person will have no effect on
the vote on adjournment, except to reduce the total number of votes counted.
Brokers who hold shares in street name for customers will not have the authority
to vote unless they receive specific instructions from beneficial owners. Under
Maryland law, an adjournment proposal requires the affirmative vote of a
majority of the votes cast by Columbia Bancorp stockholders present or
represented at the meeting. Therefore, broker non-votes and abstentions will
have no effect.

     Suburban Bancshares.  By signing the proxy, a Suburban Bancshares
stockholder authorizes the proxy holder to vote in his discretion regarding any
procedural motions which may come before the Suburban Bancshares meeting. For
example, this authority could be used to adjourn the meeting if Suburban
Bancshares believes it is desirable to do so. Adjournment or other procedural
matters could be used to obtain more time before a stockholder vote in order to
solicit additional proxies or to provide additional information to Suburban
Bancshares stockholders. To the extent a Suburban Bancshares stockholder intends
to vote against the merger agreement, such stockholder would have no incentive
to vote in favor of discretionary adjournment by the Suburban Bancshares board
of directors, which would allow Suburban Bancshares to adjourn the meeting in
order to solicit additional votes in favor of the merger agreement. Suburban
Bancshares has no plans to adjourn the meeting at this time, but it intends to
attempt to do so if it believes that doing so would promote stockholder
interests.

     The failure to return a proxy or to vote in person will have no effect on
the vote on adjournment, except to reduce the total number of votes counted.
Brokers who hold shares in street name for customers will not have the authority
to vote unless they receive specific instructions from beneficial owners. Under
Delaware law, an adjournment proposal requires the affirmative vote of a
majority of the votes cast by Suburban Bancshares stockholders present or
represented at the meeting. Therefore, broker non-votes and abstentions will
have no effect.

Revocation of Proxies

     A stockholder of Columbia Bancorp or of Suburban Bancshares may revoke a
proxy at any time before it is voted by:

     .   filing written notice of revocation with the Secretary of Columbia
         Bancorp or Suburban Bancshares (as applicable) which is actually
         received prior to the vote of stockholders;

     .   following the instructions received from their broker for any shares
         held by the broker in street name;

     .   filing a duly executed proxy bearing a later date; or

     .   attending the Columbia Bancorp or Suburban Bancshares meeting (as
         applicable) and voting in person. Attendance at the meeting will not by
         itself revoke the proxy.

                                      -35-
<PAGE>

     A Columbia Bancorp stockholder should send any such filing to the Secretary
of Columbia Bancorp at Columbia Bancorp, 9171 Baltimore National Pike, Ellicott
City, Maryland  21042, Attn.:  John A. Scaldara, Jr.  A Suburban Bancshares
stockholder should send any such filing to the Secretary of Suburban Bancshares
at Suburban Bancshares, Inc., 7505 Greenway Center Drive, P. O. Box 298,
Greenbelt, Maryland  20768-0298, Attn.:  Stephen A. Horvath.

     If you hold your shares in street name, please see the instructions
provided by your broker regarding revocation of your proxy.  If you vote your
shares through your broker, you may not change or revoke your vote by contacting
Columbia Bancorp or Suburban Bancshares directly.  You will need additional
documentation from your broker to vote your shares in person at the meeting if
they are held in street name.

Solicitation of Proxies

     We will each bear our own cost of soliciting proxies from our stockholders.
In addition to solicitation by mail, our directors, officers and employees may
solicit proxies from our stockholders by telephone or personal communication or
by other means. These persons will not receive additional compensation, but they
may be reimbursed for reasonable out-of-pocket expenses in connection with this
solicitation.

     We will make arrangements with brokerage houses and other custodians,
nominees and fiduciaries to forward solicitation materials to the beneficial
owners of Columbia Bancorp and Suburban Bancshares stock held of record by such
persons, and we will each reimburse custodians, nominees and fiduciaries for
their reasonable out-of-pocket expenses in connection with this service.

     We may engage one or more proxy solicitation firms to assist in obtaining
proxies from our stockholders on a timely basis.  As of the date of this proxy
statement/prospectus, neither of us has engaged a proxy solicitation firm or has
committed itself to pay any fees related to this service.


                                      -36-
<PAGE>

                             PARTIES TO THE MERGER

Columbia Bancorp

     Columbia Bancorp, a bank holding company, was incorporated in November 1987
under the laws of Maryland and registered as a bank holding company under the
Bank Holding Company Act of 1956, as amended.  Columbia Bank was organized by
Columbia Bancorp as a Maryland commercial bank and began operations in May 1988.
Columbia Bank currently accounts for substantially all of Columbia Bancorp's
assets.  The deposits of Columbia Bank are insured by the FDIC. Columbia Bank is
headquartered in Columbia, Maryland and has nine branch locations in Howard
County, Maryland; three branch locations in Baltimore County, Maryland; and two
branch locations in Baltimore City, Maryland.  An additional branch location is
scheduled to open before December 31, 1999 in Baltimore County, Maryland.
Columbia Bank also has three mortgage origination offices in Howard, Montgomery
and Baltimore Counties, Maryland.  At September 30, 1999, Columbia Bancorp had
total assets of $460.1 million, total loans, net of unearned income, of $305.3
million, total deposits of $354.0 million and stockholders' equity of $39.9
million.

     Columbia Bank is an independent, community bank which seeks to provide
personal attention and professional financial services to its customers while
offering virtually all of the banking services of larger competitors.  These
customers are primarily individuals and small- and medium-sized businesses.
Columbia Bank's business philosophy includes offering informed and courteous
service, local and timely decision-making, flexible and reasonable operating
procedures and consistently-applied credit policies.  Columbia Bank does not
currently exercise general trust powers.

     Columbia Bank offers the following types of services:

     Commercial Services:

     .  loans, including working capital loans and lines of credit, a wide range
        of demand, term, and time loans, loans for real estate acquisition,
        development and construction and equipment, inventory and accounts
        receivable financing

     .  lease financing

     .  cash management, including automatic overnight investment of funds

     .  certificates of deposit and other interest-bearing accounts

     .  direct deposit of payroll

     .  letters of credit



                                      -37-
<PAGE>

     Retail Services:

     .  transaction accounts, including checking and NOW accounts

     .  savings accounts

     .  certificates of deposit

     .  individual retirement accounts

     .  24-hour automated teller machines with access to major network systems

     .  24-hour telephone banking

     .  PC - Banking

     .  installment and home equity loans and lines of credit

     .  residential construction and first mortgage loans

     .  VISA(R) credit and debit cards

     .  travelers checks, money orders and safe deposit boxes

     .  internet banking (expected to be available prior to December 31, 1999)

     At September 30, 1999, Columbia Bancorp's loan portfolio, net of unearned
income, totaled $305.3 million, representing approximately 66.4% of its total
assets of $460.1 million.  The categories of loans in Columbia Bancorp's
portfolio are commercial, real estate development and construction, residential
real estate mortgage, commercial real estate mortgage and consumer.

     The executive offices of Columbia Bancorp and the principal office of
Columbia Bank are located at 10480 Little Patuxent Parkway, Columbia, Maryland
21044, telephone number (410) 465-4800.

Suburban Bancshares

     Suburban Bancshares, a bank holding company, was incorporated in 1985 under
the laws of the State of Delaware and registered as a bank holding company under
the Bank Holding Company Act of 1956, as amended.  Suburban Bank was organized
by Suburban Bancshares as a Maryland  commercial bank and began operations in
1980.

     Suburban Bank currently accounts for substantially all of Suburban
Bancshares's assets.  The deposits of Suburban Bank are insured by the FDIC.
Suburban Bank, headquartered in Greenbelt, Maryland, has a total of eight branch
locations and a mortgage lending office located in the Maryland suburbs of
Washington, D.C., in the communities of Greenbelt, Capitol Heights, Clinton,
Oxon Hill, Rockville, Bethesda, White Flint and Beltsville. Suburban Bancshares'
primary markets are the counties

                                      -38-
<PAGE>

of Prince George's and Montgomery. Suburban Bancshares also serves the
surrounding counties in Maryland and the District of Columbia. As of September
30, 1999, Suburban Bancshares had total assets of $222.8 million, total deposits
of $187.7 million, total loans, net of unearned income of $136.8 million and
total stockholders' equity of $20.4 million.

                                      -39-
<PAGE>

                                  THE MERGER

Background of the Merger

     Management of each company, has, over time, regularly considered the
possibility of acquisitions and strategic combinations with a variety of
financial institutions, and the potential strategic fit with institutions based
on their lines of business, their management and employee cultures and their
geographic locations.  As part of our operations, Columbia Bancorp and Suburban
Bancshares also regularly scrutinize the financial services industry
environment, including the recent wave of consolidation in the industry, and
from time to time have informal discussions with the management of various
financial institutions.

     In December 1998, Suburban Bancshares' board of directors appointed a
committee to evaluate any offers to merge with or acquire Suburban Bancshares
and to identify and analyze possible merger and acquisition opportunities for
Suburban Bancshares.  Danielson Associates, Inc. was asked to review ways for
Suburban Bancshares to maximize stockholder value, which included the
possibility of a sale of Suburban Bancshares.

     At a January 19, 1999 meeting of the committee, Danielson Associates
presented its analysis, which indicated that Suburban Bancshares could increase
stockholder value substantially faster through a sale and that the number of
potential acquirers that would be both compatible and pay a fair price was
rapidly diminishing as a result of consolidations in the banking industry.  As a
result of that meeting, the committee decided to determine the interest of
several potential acquirers.  In February 1999, Suburban Bancshares retained
Danielson Associates to assist it in exploring its merger opportunities.

     In consultation with Danielson Associates, the committee determined that
there were three banks that might be interested in Suburban Bancshares and had
the ability to pay a fair price that would be attractive to stockholders.  They
were all Maryland banks and included a bank with assets of over $5 billion,
another in the $1 to $2 billion asset range, and Columbia Bancorp, which was
considerably smaller than the other two.  Other banks were considered, but the
committee did not feel that any of these were likely to make a competitive
offer.

     On March 1, 1999, the committee met to consider responses from Columbia
Bancorp and one of the other potential acquirers.  The third bank chose not to
submit a bid.  At that time, the committee determined that the offers from the
two banks did not provide a sufficient premium over the prevailing market price
for Suburban Bancshares common stock.

     In August 1999, the committee decided that in light of recent developments
in the banking industry and the downward pressure on the market price of bank
stocks, including Suburban Bancshares', the sale possibilities for Suburban
Bancshares merited reconsideration by the committee.  In particular, there was
concern about increasing competition for loan and deposit customers and the
resulting pressures on margins and the growing cost of technology.  In addition,
the likely elimination of pooling of interest accounting, which could have a
negative effect on the sale value of Suburban Bancshares, had become a greater
certainty.  The committee then asked Danielson Associates to contact both of the
previous bidders to determine their present interest.


                                      -40-
<PAGE>

     Both parties had a continued interest and on September 9, 1999, the
committee met to review updated offers.  Danielson Associates presented its
independent analysis of the two offers.  After a thorough review and discussion,
the committee determined that the Columbia Bancorp offer was more favorable and
voted unanimously to recommend to the Suburban Bancshares' board of directors
that they accept the Columbia Bancorp offer.

     On September 11, 1999, the Suburban Bancshares board of directors met to
consider the two offers. Danielson Associates explained their analysis of both
offers and why the banks that were approached were considered to be the most
likely to meet the best interests of the Suburban Bancshares stockholders.
After due deliberation, the Suburban Bancshares board of directors voted
unanimously to accept the Columbia Bancorp offer.  As a result, Suburban
Bancshares and Columbia Bancorp executed a confidentiality agreement regarding
the sharing of confidential information and began the due diligence process.

     In September 1999, senior executives of Columbia Bancorp arranged to
receive proposals from several investment banks to serve as financial advisor to
Columbia Bancorp in connection with a possible transaction with Suburban
Bancshares.  On September 19, 1999, Columbia Bancorp and Austin Financial
executed an engagement letter for Austin Financial to conduct due diligence in
connection with the possible transaction and render a fairness opinion to the
Columbia Bancorp board of directors.

     The two companies and their respective legal and financial advisors began
conducting mutual due diligence.  Messrs. Bond and Kelly met to discuss the
results of the due diligence and each indicated his interest in continuing to
pursue a business combination between their companies.  Over the next several
days, senior management of the two companies and their respective legal counsel
negotiated the terms of the proposed agreements.

     On September 27, 1999, Columbia Bancorp's board of directors held a special
meeting to consider the proposed merger with Suburban Bancshares.  At this
meeting, senior management of Columbia Bancorp, together with accounting and
legal advisors, reviewed the strategic investigation and due diligence Columbia
Bancorp had conducted, the discussions and contacts with Suburban Bancshares to
date, the historical performance and strategies of Suburban Bancshares and
Columbia Bancorp, the financial and other terms of the proposed transaction,
including the potential pro forma impact of the merger (taking into account
possible expense savings and operating efficiencies that might be generated by
the transaction) and the proposed numerical composition of the new Columbia
Bancorp board of directors, and the other terms of the proposed merger
agreement, the stock option agreement and other agreements.

     Austin Financial, based on the financial analysis described under "Opinion
of Columbia Bancorp's Financial Advisor", gave its opinion to Columbia Bancorp's
board of directors that, as of the date of the meeting, the proposed conversion
ratio in the merger was fair, from a financial point of view, to Columbia
Bancorp and its stockholders.  Columbia Bancorp's board of directors also
reviewed the proposed employment arrangements with members of Suburban
Bancshares' senior management in connection with the proposed merger.  Twelve of
the 15 members of Columbia Bancorp's board of directors who were in attendance
voted to approve the proposed merger agreement and related transactions.  Three
members of the Columbia Bancorp board of directors voted against the proposed
merger and related transactions; however, each of these directors has signed a
support agreement whereby they agreed to vote their shares of Columbia Bancorp
common stock in favor of the merger agreement and related transactions.
Subsequently, the three members of the Columbia Bancorp board of directors who
voted against the merger and related transactions as well as the director who
was absent

                                      -41-
<PAGE>

from the board of directors' meeting indicated in writing that they desired
their vote to be recorded as in favor of the merger agreement and related
transactions, thus causing the vote to be unanimous.

     On September 27, 1999, the Suburban Bancshares board of directors held a
special meeting at which senior management of Suburban Bancshares reviewed its
discussions and negotiations with Columbia Bancorp regarding a business
combination, as well as the results of its due diligence investigation of
Columbia Bancorp.  Mr. Kelly reviewed Suburban Bancshares' board of directors'
prior discussions of possible strategic directions for Suburban Bancshares,
reviewed the course of discussions with Columbia Bancorp and outlined the
strategic rationale for the proposed merger.  Danielson summarized certain
financial information with respect to Columbia Bancorp and the potential
transaction to the Suburban Bancshares board of directors, and Danielson
rendered an opinion that, as of September 27, 1999, the conversion ratio set
forth in the merger agreement was fair to Suburban Bancshares' stockholders from
a financial point of view.  Also at this meeting the Suburban Bancshares board
of directors discussed with representatives of McNamee, Hosea, Jernigan & Kim,
P.A., Suburban Bancshares legal counsel, the terms of the merger and the
definitive agreements documenting the transaction, and the legal standards
applicable to its decision to approve these agreements and the transactions
contemplated by these agreements.  After questions by, and discussion among, the
members of the Suburban Bancshares board of directors, and after consideration
of the factors described under "-Suburban Bancshares Reasons for the Merger" the
Suburban Bancshares board of directors voted unanimously to approve the merger
agreement and the transactions contemplated by that agreement.

     On September 28, 1999, representatives of Columbia Bancorp and Suburban
Bancshares executed and delivered the merger agreement and stock option
agreements.  On September 28, 1999, Columbia Bancorp and Suburban Bancshares
issued a joint press release announcing the transaction.

     As provided for in the merger agreement, representatives of the two
companies continued due diligence review of the loan portfolios of each company.
Each company was given full access to loan files and records of the other
company.  Following completion of this due diligence, each company notified the
other that the due diligence requirements of Section 13(h) of the merger
agreement had been satisfied.

Suburban Bancshares Reasons for the Merger

     The members of the board of directors of Suburban Bancshares have
unanimously approved the merger agreement and the merger and have determined
that the merger is advisable and fair to, and in the best interests of, Suburban
Bancshares and its stockholders.  The Suburban Bancshares board of directors,
therefore, recommends that the holders of Suburban Bancshares common stock, vote
FOR the merger, the merger agreement and the transactions contemplated by the
merger agreement.

     The Suburban Bancshares board of directors believes that the consummation
of the merger presents a unique opportunity to combine two of the
Baltimore/Washington metropolitan area's leading community banks to create a
premier community banking and financial services company that can offer a full
range of financial products and services in the Baltimore/Washington
metropolitan area's most attractive markets.

     In reaching its decision to approve the merger agreement and the option
agreements, Suburban Bancshares' board of directors consulted with Suburban
Bancshares management, as well as with its financial and legal advisors, and
considered a number of factors, including the following:

                                      -42-
<PAGE>

     .    its knowledge of Suburban Bancshares' business, operations, financial
          condition, earnings and earnings potential, including future dividend
          payments and estimated stock value;

     .    the business, operations, financial condition and earnings of Columbia
          Bancorp. In making its determination, the board of directors took into
          account the results of Suburban Bancshares' due diligence review of
          Columbia Bancorp;

     .    the consistency of the merger with Suburban Bancshares' long-term
          goals of achieving superior financial performance and stockholder
          returns;

     .    its expectation that the combined company would benefit from
          significantly greater economies of scale than either Suburban
          Bancshares or Columbia Bancorp separately in its consumer banking,
          commercial banking and other businesses;

     .    its view that the combination of Suburban Bancshares and Columbia
          Bancorp presents manageable execution risk in view of the similar
          markets and customer demographics served by Suburban Bancshares and
          Columbia Bancorp, the complementary and contiguous geographic areas
          served by our companies and assumptions regarding synergies;

     .    its belief, and that of Suburban Bancshares' senior management, that
          Suburban Bancshares and Columbia Bancorp share a common vision about
          the importance of delivering financial performance and stockholder
          value and that management and employees of Suburban Bancshares and
          Columbia Bancorp possess complementary skills and expertise;

     .    the structure of the merger and the terms of the merger agreement and
          the stock option agreements, and the fact that the merger is intended
          to qualify as a "reorganization" for federal income tax purposes and
          as a "pooling-of-interests" for accounting and financial reporting
          purposes;

     .    the proposed arrangements with members of management of Columbia
          Bancorp and Suburban Bancshares, including the fact that Mr. Bond
          would continue as Columbia Bancorp's president and chief executive
          officer, that Mr. Kelly would enter into a services agreement with
          Columbia Bancorp and would become chairman of the board of directors
          of Columbia Bancorp; and that the board of directors of the combined
          company would be comprised of 16 directors designated by Columbia
          Bancorp and 5 directors designated by Suburban Bancshares, including
          Mr. Kelly;

     .    the fact that directors and executive officers of Suburban Bancshares
          could be expected to receive benefits in the merger beyond their
          interests as stockholders of Suburban Bancshares, both under existing
          arrangements with our company and, in the case of Mr. Kelly and one
          other executive officer of Suburban Bancshares, as a result of new
          employment agreements with Columbia Bancorp. See "-- Interests of
          Persons in the Merger Other Than as Stockholders";

                                      -43-
<PAGE>

     .    the opinion of Danielson Associates that, as of September 27, 1999,
          the conversion ratio was fair from a financial point of view to
          Suburban Bancshares stockholders. See "--Opinion of Suburban
          Bancshares' Financial Advisor"; and

     .    the likelihood that the merger will be approved by the appropriate
          regulatory authorities. See "The Merger Agreement--Regulatory
          Approvals Required for the Merger."

     The foregoing discussion of the information and factors considered by the
Suburban Bancshares board is not intended to be exhaustive but is believed to
include all material factors considered by the Suburban Bancshares board.  In
view of the variety of factors considered in connection with its evaluation of
the merger, the Suburban Bancshares board did not find it practicable to and did
not quantify or otherwise assign relative weights to the specific factors
considered in reaching its determination.  In addition, individual members of
the Suburban Bancshares board may have given different weights to different
factors.  However, after taking into account all of the factors set forth above,
the Suburban Bancshares board of directors unanimously agreed that the merger
agreement and the merger were fair to, and in the best interests of, Suburban
Bancshares and its stockholders and that Suburban Bancshares should proceed with
the merger agreement and the merger.

     The members of Suburban Bancshares' board of directors unanimously
recommend that Suburban Bancshares stockholders vote FOR approval and adoption
of the merger agreement and the merger.


Opinion of Suburban Bancshares' Financial Advisor

     Suburban Bancshares retained Danielson Associates, Inc. to advise the
Suburban Bancshares board of directors as to its "fair" sale value and the
fairness to its stockholders of the financial terms of the offer to be acquired
by Columbia Bancorp.  Danielson Associates is regularly engaged in the valuation
of banks, bank holding companies, and thrifts in the connection with mergers,
acquisitions, and other securities transactions; and has knowledge of, and
experience with, Maryland banking markets and banking organizations operating in
those markets.  Danielson Associates was selected by Suburban Bancshares because
of its knowledge of, expertise with, and reputation in the financial services
industry.

     In this capacity, Danielson Associates reviewed the merger agreement with
respect to the pricing and other terms and conditions of the merger, but the
negotiation of the merger agreement and the decision as to accepting the offer
was ultimately made by the board of directors of Suburban Bancshares.  Danielson
Associates rendered its oral opinion to the Suburban Bancshares board of
directors, which it subsequently confirmed in writing, that as of the date of
the opinion, the financial terms of the Columbia Bancorp offer were "fair" to
Suburban Bancshares and its stockholders.  No limitations were imposed by the
Suburban Bancshares board of directors upon Danielson Associates with respect to
the investigation made or procedures followed by Danielson Associates in
arriving at its opinion.

     In arriving at its opinion, Danielson Associates:

     .    reviewed certain business and financial information relating to
          Suburban Bancshares and Columbia Bancorp, including annual reports for
          the fiscal year ended December 31, 1998, call report data from 1990 to
          1999, and the Annual Reports on Form 10-K and the Quarterly Reports on
          Form 10-Q for 1998 and 1999;

                                      -44-
<PAGE>

     .    discussed the past and current operations, financial condition and
          prospects of Columbia Bancorp with its senior executives;

     .    analyzed the pro forma impact of the merger on Columbia Bancorp's
          earnings per share, capitalization, and financial ratios;

     .    reviewed the reported prices and trading activity for the Columbia
          Bancorp common stock and compared them to those of similar bank
          holding companies;

     .    reviewed and compared the financial terms, to the extent publicly
          available, with comparable transactions;

     .    reviewed the merger agreement and certain related documents; and

     .    considered such other factors as Danielson Associates deemed
          appropriate.

     Danielson Associates did not obtain any independent appraisal of assets or
liabilities of Suburban Bancshares or Columbia Bancorp or their respective
subsidiaries.  Further, Danielson Associates did not independently verify the
information provided by Suburban Bancshares or Columbia Bancorp and assumed the
accuracy and completeness of all such information.

     In arriving at its opinion, Danielson Associates performed a variety of
financial analyses.  Danielson Associates believes that its analyses must be
considered as a whole and that consideration of portions of such analyses could
create an incomplete view of Danielson Associates' opinion.  The preparation of
a fairness opinion is a complex process involving subjective judgements and is
not necessarily susceptible to partial analysis or summary description.

     In its analyses, Danielson Associates made certain assumptions with respect
to industry performance, business and economic conditions, and other matters,
many of which were beyond Suburban Bancshares' or Columbia Bancorp's control.
Any estimates contained in Danielson Associates analyses are not necessarily
indicative of the future results of value, which may be significantly more or
less favorable than such estimates.  Estimates of the value of companies do not
purport to be appraisals or necessarily reflect the prices at which companies or
their securities may actually be sold.

     The following is a summary of selected analyses considered by Danielson
Associates in connection with its opinion letter.

     Pro Forma Merger Analyses.  Danielson Associates analyzed the changes in
the amount of earnings and book value represented by the receipt of
approximately $34 million for all of the outstanding shares of Suburban
Bancshares common stock and options to purchase shares of Suburban Bancshares
common stock, which will be paid in shares of Columbia Bancorp common stock or
options to purchase shares of Columbia Bancorp common stock.  The analysis
evaluated, among other things, possible dilution in earnings and capital per
share for Columbia Bancorp common stock.

     Comparable Companies.  Danielson Associates compared Columbia Bancorp to 12
publicly-traded bank holding companies.  These comparable bank holding companies
had assets in the $300 million to $2 billion range, no extraordinary
characteristics and were located in urbanized portions of Maryland and eastern
Pennsylvania.

                                      -45-
<PAGE>

         SUMMARY AND DESCRIPTION OF COMPARABLE BANK HOLDING COMPANIES
<TABLE>
<CAPTION>
     Comparable Bank Holding Companies                           Assets/(1)/          Headquarters
     ---------------------------------                           -----------          -------------
                                                                 (In millions)
     <S>                                                         <C>                  <C>
     Bryn Mawr Bank Corp.                                           $  393            Bryn Mawr, Pa.
     Carrollton Bancorp                                                346            Baltimore, Md.
     Community Banks, Inc.                                             917            Millersburg, Pa.
     Drovers Bancshares Corp.                                          643            York, Pa.
     F&M Bank Corp.                                                  1,462            Frederick, Md.
     FCNB Corp.                                                      1,328            Frederick, Md.
     First Colonial Group, Inc.                                        384            Nazareth, Pa.
     Harleysville Savings Bank                                       1,509            Harleysville, Pa.
     Pennsylvania Commerce Bancorp                                     350            Camp Hill, Pa.
     Sandy Springs Bancorp, Inc.                                     1,335            Olney, Md.
     Sterling Bancorp                                                1,031            Lancaster, Pa.
     Union National Bancorp                                            300            Westminster, Md.
</TABLE>

__________________

(1)      June 30, 1999.

       Source: SNL Securities LC, Charlottesville, Virginia.


       Danielson Associates compared the medians of the following ratios between
comparable bank holding companies and Columbia Bancorp, and also compared other
income, expense and balance sheet information of these companies with similar
information about Columbia Bancorp.

                                      -46-
<PAGE>

         COLUMBIA BANCORP - COMPARABLE BANK HOLDING COMPANIES SUMMARY

<TABLE>
<CAPTION>
                       Income                                     Columbia Bancorp             Companies Median
                       ------                                     ----------------             ----------------
   <S>                                                            <C>                          <C>
   Net income/Avg. Assets                                              1.17%                           .99%
   Net operating income/(1)//Avg. Assets                               1.97                           1.54
   Return on average equity                                           13.14                          13.03

   Balance Sheet

     Equity/Assets                                                     8.53%                          8.07
     NPAs/(2)//Assets                                                   .84                            .37

   Stock Price
     Price/Earnings                                                   11.9X                          14.2X
     Price/Book                                                         149%                           201%
     Dividend yield                                                    2.48%                          2.91%
     Payout ratio                                                        28%                            40%
     Shares traded/(3)/                                               6,870                          2,204
</TABLE>

     __________

     (1) Net interest income plus noninterest income less operating expense.

     (2) Nonperforming assets including loans 90 days past due and still
         accruing.

     (3) Average daily volume in 1999 through September 27, 1999.

     Source:  SNL Securities LC, Charlottesville, Virginia.


     Comparable Transaction Analysis.  Danielson Associates compared the
consideration to be paid in the merger to the latest 12 months' earnings and
equity capital of Suburban Bancshares with earnings and capital multiples paid
in acquisitions of banks through September 27, 1999 in Delaware, Washington
D.C., Maryland and Virginia.  Of these, the most applicable recent transactions
(because of the similar size of the acquired bank) included BB&T Corporation's
purchase of Mason-Dixon Bancshares, Inc., F&M Bancorp's acquisition of Monocacy
Bancshares, Inc. and FCNB Corp.'s purchase of Capital Bank NA.  At the time
Danielson Associates made its analysis, the consideration to be paid in the
merger was 166% of Suburban Bancshares' June 30, 1999 book value, 23.8 times
Suburban Bancshares' "normalized" earnings for the 12 months ending June 30,
1999, and 27.2 times reported earnings for the trailing four quarters as of June
30, 1999.  This compares to the median multiples of 265% of book value and 22.5
times earnings for the three most applicable recent transactions.

     Discounted Future Earnings and Discounted Dividends Analysis.  Danielson
Associates applied present value calculations to Suburban Bancshares' estimated
future earnings and dividend stream under several specific growth and earnings
scenarios.  This analysis considered, among other things, scenarios for Suburban
Bancshares as an independent institution and as part of another banking
organization.  The projected dividend streams and terminal values, which were
based on a range of earnings multiples, were then discounted to present value
using discount rates based on assumptions regarding the rates of return required
by holders or prospective buyers of shares or Suburban Bancshares common stock.

                                      -47-
<PAGE>

     Other Analysis.  In addition to performing the analyses summarized above,
Danielson Associates also considered the general market for bank mergers, the
historical financial performance of Suburban Bancshares and Columbia Bancorp,
the market positions of both companies and the general economic conditions and
prospects of those companies.

     No company or transaction used in this composite analysis is identical to
Suburban Bancshares or Columbia Bancorp.  Accordingly, an analyses of the
results of the foregoing is not mathematical; rather it involves complex
considerations and judgements concerning differences in financial and operating
characteristics of the companies and other factors that could affect the public
trading values of the company or companies to which they are being compared.

     The summary set forth above does not purport to be a complete description
of the analyses and procedures performed by Danielson Associates in the course
of arriving at its opinions.  In payment for its services as the financial
advisor to Suburban Bancshares, Danielson Associates is to be paid an estimated
fee of approximately $169,500.

     The full text of the opinion of Danielson Associates dated as of September
28, 1999, which sets forth assumptions made and matters considered, is attached
hereto as Appendix G of this proxy statement/prospectus.  Suburban Bancshares
stockholders are urged to read this opinion in its entirety.  Danielson
Associates' opinion is directed only to the consideration to be received by
Suburban Bancshares stockholders in the merger and does not constitute a
recommendation to any Suburban Bancshares stockholder as to how such stockholder
should vote at the Suburban Bancshares stockholder meeting.

Columbia Bancorp Reasons for the Merger

     The Columbia Bancorp board of directors believes that the merger is
advisable and in the best interests of Columbia Bancorp and its stockholders and
approved the merger agreement and the merger. Columbia Bancorp's board of
directors believes that the opportunities created by the merger to increase the
value of the Columbia Bancorp common stock more than offset any risks inherent
in the merger. In reaching this decision, Columbia Bancorp's board of directors
evaluated the information at its disposal, consulted with Columbia Bancorp's
management and outside advisors, and considered certain factors, including the
following:



     .    the complementary and compatible nature of Columbia Bancorp's and
          Suburban Bancshares' businesses in contiguous markets. The board of
          directors of Columbia Bancorp specifically considered the current
          businesses, operations, financial condition and earnings of Suburban
          Bancshares, as well as the future prospects of Suburban Bancshares. In
          making its determination, Columbia Bancorp's board of directors took
          into account the results of its due diligence investigation of
          Suburban Bancshares;

     .    an increase in the total assets of Columbia Bancorp of 48.4% to $682.9
          million, reflecting 41,000 households and businesses served;

     .    expansion geographically of Columbia Bancorp's branch network to
          include Prince George's County and Montgomery County, Maryland,
          representing markets with strong business and retail demographics and
          markets with which Columbia Bancorp is familiar as

                                      -48-
<PAGE>

          a result of existing lending activities. Columbia Bancorp will operate
          23 banking offices, inclusive of its branch facility in Baltimore
          County, Maryland scheduled to open in December 1999;

     .    the opportunity to provide customers and prospects of Columbia Bancorp
          and Suburban Bancshares a broader array of financial services. In
          particular, Columbia Bancorp's consumer banking capabilities will
          greatly enhance the current consumer banking capabilities of Suburban
          Bancshares. In addition, Suburban Bancshares is a Preferred Lender of
          the Small Business Administration. Columbia Bancorp currently does not
          have that status;

     .    diversification of Columbia Bancorp's revenue and earnings mix. In
          particular, the merger will increase Columbia Bancorp's commercial
          loan portfolio. Commercial loans, inclusive of commercial mortgages,
          will increase from 31.1% of total loans (Columbia Bancorp as of
          September 30, 1999) to ___% (pro forma as of September 30, 1999);

     .    the expectation that the combined company could realize significant
          operating synergies, estimated at $____ million (pre-tax) annually by
          the end of the fiscal year 2000; and

     .    the opinion of its financial advisor, Austin Financial, which
          indicated that the conversion ratio, as of September 24, 1999, was
          fair from a financial point of view to Columbia Bancorp's
          stockholders.

     The foregoing discussion of the information and factors considered and
given weight by Columbia Bancorp's board of directors is not intended to be
exhaustive.  In reaching the determination to approve and recommend approval and
adoption of the merger agreement, in view of the wide variety of factors
considered in connection with its evaluation thereof, the board of directors of
Columbia Bancorp did not assign any relative or specific weights to the
foregoing or other factors, and individual directors may have given different
weights to the various factors. The terms of the merger were the result of
arm's-length negotiations between representatives of Suburban Bancshares and
representatives of Columbia Bancorp. Based upon the consideration of the
foregoing factors, the Columbia Bancorp board of directors approved the merger
agreement and the transactions contemplated thereby as being advisable and in
the best interests of Columbia Bancorp and its stockholders.

     The members of Columbia Bancorp's board of directors have unanimously
declared the merger advisable and recommend that Columbia Bancorp stockholders
vote in favor of the merger agreement and the merger.

Opinion of Columbia Bancorp's Financial Advisor

     At the request of the Columbia Bancorp board, Austin Financial delivered a
written opinion to the board of directors on September 24, 1999, that the merger
consideration was fair to Columbia Bancorp's stockholders from a financial point
of view. The terms of the merger were the result of arm's-length negotiations
between representatives of Suburban Bancshares and representatives of Columbia
Bancorp.

                                      -49-
<PAGE>

     The full text of the Austin Financial opinion is attached to this proxy
statement/prospectus as Appendix F.  The full text of the Austin Financial
opinion includes the assumptions made by Austin Financial in arriving at its
opinion as well as certain qualifications to the opinion of Austin Financial.
Furthermore, the full text of the Austin Financial opinion describes the
information reviewed by Austin Financial and briefly describes the
qualifications of Austin Financial to render an opinion as to the fairness, from
a financial point of view, of the merger to Columbia Bancorp's stockholders.
This summary of the Austin Financial opinion is qualified in its entirety by
reference to the full text of the Austin Financial opinion.

     Austin Financial believes that its analyses must be considered as a whole
and that selecting portions of its analyses and the factors considered by it,
without considering all analyses and factors, could create a misleading or
incomplete view of the processes underlying such analyses and its opinion.  The
following is a summary of the written report prepared by Austin Financial for
Columbia Bancorp's board of directors:

     In connection with its opinion, Austin Financial, among other things:

     .    reviewed the Annual Report of Suburban Bancshares for the year ending
          1998;

     .    reviewed the Consolidated Reports of Condition and Income of Suburban
          Bancshares for the years ending 1994-1998 and for June 30, 1999;

     .    reviewed the Quarterly report on Form 10-Q of Suburban Bancshares for
          June 30, 1999;

     .    reviewed the Uniform Bank Performance Report of Suburban for June 30,
          1999;

     .    reviewed the investment security portfolio of Suburban Bancshares as
          of August 31, 1999;

     .    reviewed the statement of financial condition of Suburban Bancshares
          as of August 31, 1999;

     .    reviewed the rate sensitivity analysis data of Suburban Bancshares'
          loan portfolio as of August 31, 1999;

     .    reviewed the interest rate schedule for Suburban Bancshares as of
          September 14, 1999;

     .    reviewed Suburban Bancshares' stock price history from July 1, 1999 to
          September 16, 1999;

     .    reviewed the trial balance of Suburban Bancshares as of August 31,
          1999;

     .    reviewed the classified assets and loan watch list of Suburban as of
          August 31, 1999;

     .    reviewed the nonaccrual loan list of Suburban Bancshares as of August
          31, 1999;

     .    reviewed the depreciation projections for Suburban Bancshares for the
          years 2000-2004;

     .    reviewed other internal financial and operating information which was
          provided by Suburban Bancshares;

                                      -50-
<PAGE>

     .    reviewed publicly available information concerning certain other banks
          and thrifts and bank and thrift holding companies, the trading markets
          for their securities and the nature and terms of certain other merger
          and acquisition transactions believed relevant to its inquiry;

     .    reviewed the reported price and trading activity for Columbia
          Bancorp's common stock;

     .    reviewed certain financial and stock market information for Columbia
          Bancorp and Suburban Bancshares with similar information of certain
          other financial institutions whose securities are publicly traded;

     .    held discussions regarding the foregoing, as well as other matters
          relevant to Austin Financial's inquiry, including the past and current
          business operations and acquisitions, results of regulatory
          examinations, financial condition, current loan quality and trends,
          and future prospects of Suburban Bancshares with certain officers and
          representatives of Suburban Bancshares;

     .    reviewed the merger agreement; and

     .    performed such other studies and analyses as Austin Financial
          considered appropriate.

     Discounted Cash Flow Analysis.  Austin Financial performed a discounted
cash flow analysis for the Suburban Bancshares common stock on a stand-alone
basis from August 31, 2000 through August 31, 2004, assuming a minimum equity
capital to asset ratio of 6%.  Austin Financial estimated the residual value of
Suburban Bancshares' common equity as of August 31, 2004.  The present value per
share currently outstanding of Suburban Bancshares' common stock resulting from
this analysis was $3.21 (assuming 11,301,218 shares outstanding).

     Adjusted Book Value Analysis.  Austin Financial determined the adjusted
book value of Suburban Bancshares as an alternative valuation method.  This
analysis determined that the fair market value per share currently outstanding
of Suburban Bancshares common stock was $2.71.

     Selected Merger and Acquisition Transactions.  Austin Financial analyzed
certain other mergers and acquisitions that have been completed over the past
eight months in Maryland as well as other nearby states (including the states of
Delaware, West Virginia, New Jersey, Pennsylvania and Virginia) involving target
financial institutions with assets under $700 million. Austin Financial compared
the multiple produced by this reorganization to the mean multiples for the
transactions analyzed. The mean transaction multiples are in the table below:

<TABLE>
<CAPTION>
                                       Selected Bank/Thrift
                                           Acquisitions        Suburban Bancshares
                                           ------------        -------------------
     <S>                               <C>                     <C>
     Price/Earnings Multiple                   27.73                   28.61
     Price/Book Value Multiple                197.42                  161.11
</TABLE>

     In reaching its opinion as to the fairness, Austin Financial applied a 75%
weighting to the discounted cash flow value and a 25% weighting to the adjusted
book value analyses.  The weightings

                                      -51-
<PAGE>

were based on Austin Financial's review of the financial position, history and
recent performance of Suburban Bancshares. The sum of the weighted values or
$3.08 per share equates to the fair market value of Suburban Bancshares. Based
on the terms of the merger agreement, a closing price per share of $13.0625 for
Columbia Bancorp's common stock on September 23, 1999, would result in a $3.00
per share value for Suburban Bancshares' stockholders. As a result of its
consideration of the aggregate of all factors present and analyses performed,
Austin Financial reached the conclusion, and opined, that the conversion ratio
pursuant to the merger agreement was fair to the stockholders of Columbia
Bancorp from a financial point of view.

     Austin Financial's September 24, 1999 opinion was based solely upon the
information available to it and the economic, market and other circumstances as
they existed and could be evaluated as of the date its opinion was delivered;
events occurring after the date of its September 24, 1999 opinion could
materially affect the assumptions used in preparing its opinion.  Austin
Financial has not undertaken to reaffirm and revise its September 24, 1999
opinion or otherwise comment upon any events occurring after that date.

     Columbia Bancorp retained Austin Financial based upon its banking
experience and expertise.  Austin Financial is a nationally recognized
investment banking firm specializing in the banking and financial services
industry.  Austin Financial is continually engaged in the valuation of
businesses and securities in connection with mergers and acquisitions, private
placements and valuations for estate, corporate and other purposes.

     Columbia Bancorp's board of directors engaged Austin Financial to render an
opinion in connection with the board's discharge of its fiduciary obligations.
The terms of the merger were the result of arm's-length negotiations between
representatives of Suburban Bancshares and representatives of Columbia Bancorp.
Austin Financial has advised the board of directors that it does not believe
that any person, including a stockholder of Columbia Bancorp, other than the
board of directors has the legal right to rely upon the opinion for any claim
arising under state law and that, should any claim be brought against it, it
will raise this assertion as a defense.  Resolution of this matter under state
law, however, will have no effect on the rights and responsibilities of any
person under the federal securities laws or on the rights and responsibilities
of Columbia Bancorp.

     Pursuant to the terms of an engagement letter dated September 19, 1999,
Columbia Bancorp agreed to pay Austin Financial for acting as financial advisor
to the board of directors in connection with the merger a fee of $17,500, plus
expenses, payable in cash upon delivery of the opinion.

     In addition, Columbia Bancorp has agreed to indemnify Austin Financial and
certain related persons against certain liabilities relating to or arising out
of its engagement, including certain liabilities under the federal securities
laws.

Interests of Persons in the Merger Other Than as Stockholders

     Some officers and directors of Suburban Bancshares have interests in the
merger in addition to their interests as stockholders. The board of directors of
each of the companies was aware of these interests and took these interests into
account in approving the merger agreement and the transactions contemplated
thereby. These interests include, among other things:

                                      -52-
<PAGE>

     .    the appointment of Winfield Kelly, Albert Turner, Lawrence Shulman,
          Vincent Palumbo and Kenneth Michael, who are currently serving as
          directors of Suburban Bancshares, to the Columbia Bancorp board of
          directors after the merger;

     .    execution of certain employment and services agreement with certain
          members of Suburban Bancshares' management team, including without
          limitation, Messrs. Kelly and Horvath;

     .    the continuation of the indemnification rights and liability insurance
          of directors and officers of Suburban Bancshares.

     Composition of Columbia Bancorp's Board Following the Merger.   In
connection with the merger and the transactions contemplated thereby, Columbia
Bancorp agreed to cause its board of directors, consistent with their fiduciary
duties and in accordance with Maryland law, to appoint Messrs. Kelly, Turner,
Schulman, Palumbo and Michael, currently members of Suburban Bancshares' board
of directors, to become members of Columbia Bancorp's and Columbia Bank's board
of directors promptly after the effective time of the merger (as defined below
in "-- Effective Time of the Merger").  Mr. Kelly will serve as Chairman of the
Board of Directors and as Chairman of the Board of Directors of Columbia Bank.
There are no agreements or understandings regarding the re-nomination or re-
election of any of the Suburban Bancshares' directors or directors of Columbia
Bancorp after the expiration of their initial terms.  Messrs. Kelly and Turner
will be appointed to the class of directors of Columbia Bancorp serving until
2002, Messrs. Schulman and Palumbo to the class of directors of Columbia Bancorp
serving until 2001 and Mr. Michael to the class of directors of Columbia Bancorp
serving until 2000.

     Employment and Services Agreements.  Pursuant to a services agreement
between Columbia Bancorp and Winfield M. Kelly, Jr., Mr. Kelly will serve as the
Chairman of the board of directors of the Columbia Bancorp and as Chairman of
the board of directors of Columbia Bank.  Under the services agreement Mr. Kelly
will receive (i) annual director's fees of $60,000, and (ii) certain employee
benefits. The term of the amended agreement will expire upon the expiration of
Mr. Kelly's initial term as a director of Columbia Bancorp and is subject to
automatic renewal upon his re-election as Chairman of the Board by the board of
directors.  If the agreement is terminated by Columbia Bancorp without cause or
if Mr. Kelly terminates the agreement for "cause", Columbia Bancorp must pay Mr.
Kelly the sum of $120,000 as severance compensation.  If Mr. Kelly's agreement
is terminated by Columbia Bancorp for "cause", he will be entitled only to
compensation earned prior to such termination.  Upon the earlier of (i) five
years from the effective date of the merger or (ii) in the event the agreement
is terminated or not renewed as a result of any sale or exchange of stock
resulting in a change in a controlling interest of Columbia Bancorp or Columbia
Bank, Columbia Bancorp will pay Mr. Kelly $200,000 as additional compensation.

     Under the terms of his employment agreement, Stephen A. Horvath will serve
as the Executive Vice President - Washington Region of Columbia Bank with a
minimum annual base compensation of $150,000, which is subject to normal
periodic review, at least annually, for increases based on the salary policies
of Columbia Bank and Mr. Horvath's contribution to Columbia Bank.  The terms of
Mr. Horvath's employment agreement continue until the earlier of (i) the close
of business on the date which is two years after the date on which either party
provides written notice of termination, other than for "cause", as defined in
the employment agreement, but no later than the close of business on the sixty-
fifth birthday of Mr. Horvath, or (ii) the date on which Mr. Horvath's
employment is otherwise terminated pursuant to the terms of the employment
agreement.  Mr. Horvath is also entitled to participate in all incentive and
benefit programs offered by Columbia Bank.  If Mr. Horvath's employment is
terminated,

                                      -53-
<PAGE>

other than for "cause", Columbia Bank is required to continue to provide
benefits to him and pay his salary for two years. The employment agreement also
contains a non-competition provision which prohibits Mr. Horvath during his
employment with Columbia Bank or for a period of two years following voluntary
resignation or termination for "cause", from directly or indirectly engaging in
activities competitive with the business of Columbia Bank.

     The Agreement also provides that in the event of (i) termination, other
than for "cause", (ii) resignation due to a significant change in the nature or
scope of authority and duties, or (iii) resignation as a result of not having
been offered a new employment agreement with similar terms, 90 days prior to, or
within one year after, any "change in control" (as defined in the employment
agreement) of Columbia Bank, Mr. Horvath, within 15 days of termination, will be
paid a lump sum payment equal to two times the sum of his annual base
compensation and the average of the bonuses paid to him over the past two years.
In the event of voluntary resignation 90 days prior to, or within one year
after, any "change in control" of Columbia Bank, Mr. Horvath, within 15 days of
resignation, will be paid a lump sum payment equal to the sum of his annual base
salary and the average of the bonuses paid to him over the past three years. Any
payments made in connection with a "change in control" of Columbia Bank after
Mr. Horvath reaches 63 years of age will be pro-rated to age 65.  In addition,
if within one year of Mr. Horvath's employment he resigns for any reason,
Columbia Bank will pay him a lump sum of $150,000.

Form of the Merger

     If (i) a majority of the holders of Suburban Bancshares common stock
approve the merger agreement, (ii) two-thirds of the Columbia Bancorp
stockholders approve the merger agreement, and (iii) all other conditions to the
merger are satisfied or waived, where permissible, Suburban Bancshares will be
merged with and into Columbia Bancorp, with Columbia Bancorp being the surviving
corporation after the merger. In the merger, each share of Suburban Bancshares
common stock will be exchanged for shares of Columbia Bancorp common stock
equivalent to an average market value of $3.00 per share.  The conversion ratio
necessary to cause the average market value of shares of Columbia Bancorp common
stock exchanged for each share of Suburban Bancshares common stock to be $3.00
per share will continually change until the merger is completed, except that the
conversion ratio will not be above 0.2338 nor below 0.2196. Columbia Bancorp's
current bylaws and charter will become those of the surviving corporation.
Columbia Bancorp and Suburban Bancshares anticipate that the closing date will
occur as promptly as practicable after the meetings. As part of the merger,
Columbia Bank and Suburban Bank entered into a bank plan of merger.  The bank
plan of merger provides that Suburban Bank will merge into Columbia Bank.  We
expect to complete the bank merger concurrently with the completion of the
merger.

Consideration for the Merger

     The merger agreement provides that, at the effective time of the merger,
each share of Suburban Bancshares common stock will be exchanged for shares of
Columbia Bancorp common stock equivalent to an average market value of $3.00 per
share.  The conversion ratio necessary to cause the average market value of
shares of Columbia Bancorp common stock exchanged for each share of Suburban
Bancshares common stock to be $3.00 per share will continually change until the
merger is completed, except that the conversion ratio will not be above 0.2338
nor below 0.2196.  Former Suburban Bancshares stockholders will hold between
35.5% and 37.0% of the outstanding shares of Columbia Bancorp common stock after
the merger, depending on the final conversion ratio.

                                      -54-
<PAGE>

     In lieu of fractional shares of Columbia Bancorp common stock, Columbia
Bancorp will pay an amount in cash (rounded to the nearest cent) equal to the
product of (i) the fractional share interest to which a Suburban Bancshares
stockholder (after taking into account all shares of Suburban Bancshares common
stock held immediately prior to the effective time of the merger by such
stockholder) would otherwise be entitled and (ii) the average daily high and low
trade prices per share of Columbia Bancorp common stock for the 10 trading days
ending three trading days before the effective date.

     At the effective time, each Suburban Bancshares stock option, whether
vested or unvested, is to be converted into an option to purchase shares of
Columbia Bancorp common stock, with the number of shares and options prices
adjusted to give effect to the conversion rate, and will no longer represent a
right to acquire shares of Suburban Bancshares common stock.

Effective Time of the Merger

     The "effective date of the merger" will be upon the filing of articles of
merger with the Maryland Department of Assessments and Taxation and a
certificate of merger with the Secretary of State of the State of Delaware or at
such other time as specified in these filings. These filings will be made at the
same time as the closing of the merger.

Procedures for Exchange of Suburban Bancshares Stock Certificates

     Promptly after the effective date, Columbia Bancorp will send transmittal
materials to each Suburban Bancshares stockholder for use in exchanging his or
her certificates representing shares of Suburban Bancshares common stock for
shares of Columbia Bancorp common stock. Suburban Bancshares stockholders should
not surrender their certificates for exchange until they receive the letter of
transmittal and instructions. The transfer agent will deliver certificates for
Columbia Bancorp common stock and/or a check for any fractional share interests
or dividends or distributions once it receives the certificates representing a
holder's shares of Suburban Bancshares common stock. No party will be liable to
any stockholder for any amount properly delivered to a public official pursuant
to any applicable abandoned property, escheat or similar law.

     If a Suburban Bancshares stockholder requests that any cash or certificates
representing shares of Columbia Bancorp common stock be paid to or issued in a
different name, then the certificate surrendered must be properly endorsed and
the Suburban Bancshares stockholder must show that any transfer taxes have been
paid or pay the amount of such taxes to the transfer agent. Columbia Bancorp and
the transfer agent may withhold funds from consideration to be paid to any
certificate holder as required by any tax law; however, the holder will be
deemed to have received the full consideration for purposes of the merger
agreement.

     If you participate in Suburban Bancshares' Stock Purchase Plan, the
Suburban Bancshares shares held in your account under the plan will be converted
to shares of Columbia Bancorp common stock based on the conversion ratio. These
Columbia Bancorp shares will then be distributed to you after the effective date
of the merger.  Columbia Bancorp does not maintain a stock purchase plan and
will terminate Suburban Bancshares' plan upon the effective date.

     After the effective date, there will be no transfers of shares of Suburban
Bancshares common stock on Suburban Bancshares' stock transfer books. If
certificates representing shares of Suburban

                                      -55-
<PAGE>

Bancshares common stock are presented for transfer after the effective date, the
transfer agent will cancel and exchange them for certificates representing
shares of Columbia Bancorp common stock and a check for the amount to be paid
for fractional shares of Columbia Bancorp common stock, if any, and new
certificates bearing the name of the holder will be issues representing shares
of Columbia Bancorp common stock.

     You should not forward Suburban Bancshares common stock certificates to the
transfer agent until you receive a letter of transmittal.

     Fractional Shares.  Columbia Bancorp will not issue any fractional shares
of Columbia Bancorp common stock. Instead, a Suburban Bancshares stockholder who
would otherwise have received a fraction of a share of Columbia Bancorp common
stock will receive cash, without interest. The amount of cash received will be
determined by multiplying the fraction of Columbia Bancorp common stock the
stockholder would have been entitled to receive by the average daily high and
low trade prices per share of Columbia Bancorp common stock for the 10 trading
days ending three trading days before the effective date. Holders will not be
entitled to dividends, voting rights or any other rights as a stockholder with
respect to any fractional shares.

Exchange of Suburban Bancshares Stock Options

     At the effective date, each Suburban Bancshares stock option, whether
vested or unvested, is to be converted into an option to purchase shares of
Columbia Bancorp common stock and will no longer represent a right to acquire
shares of Suburban Bancshares common stock. These options will be adjusted so
that (1) the number of shares of Columbia Bancorp common stock purchasable upon
exercise of the Suburban Bancshares stock option will be equal to the number of
shares of Suburban Bancshares common stock that were purchasable under the
Suburban Bancshares stock option immediately prior to the effective time
multiplied by the conversion ratio, and rounded down to the nearest whole share,
and (2) the per share exercise price under each Suburban Bancshares stock option
will be adjusted by dividing the per share exercise price of the Suburban
Bancshares stock option by the conversion ratio, and rounding down to the
nearest cent. However, each Suburban Bancshares stock option which is intended
to be an "incentive stock option" will be adjusted in accordance with the
requirements of the Internal Revenue Code. Accordingly, with respect to any
incentive stock options, fractional shares will be rounded down to the nearest
whole number of shares and where necessary the per share exercise price will be
rounded up to the nearest cent. At or prior to the effective time, Columbia
Bancorp must take all corporate action necessary to reserve for issuance a
sufficient number of shares of Columbia Bancorp common stock for delivery upon
exercise of the Suburban Bancshares stock options assumed by it in accordance
with the merger agreement. As soon as practicable after the effective time,
Columbia Bancorp must file a registration statement in appropriate form covering
the issuance of Columbia Bancorp common stock subject to the Suburban Bancshares
stock options that are converted pursuant to the terms of the merger.

Anticipated Accounting Treatment

     We intend for the merger to be accounted for as a pooling-of-interests in
accordance with generally accepted accounting principles. Columbia Bancorp will
restate, retroactively at the effective time of the merger, its consolidated
financial statements to include the assets, liabilities, stockholders' equity
and results of operations of Suburban Bancshares, subject to any adjustments
required to conform with the accounting policies and financial statement
classifications of the two companies, as if the

                                      -56-
<PAGE>

companies had been combined at the first date covered by the combined financial
statements. In future financial statements, the results of operations of the
combined entity will include the results of both Columbia Bancorp and Suburban
Bancshares for the entire fiscal year in which the merger occurs and all prior
fiscal periods presented therein.

     The unaudited pro forma combined condensed financial data contained in this
proxy statement/prospectus with respect to Columbia Bancorp and Suburban
Bancshares has been prepared using the pooling-of-interests accounting method to
account for the merger.

Material Federal Income Tax Considerations

     The following is a summary of the material U.S. federal income tax
consequences to holders of Suburban Bancshares common stock who hold the stock
as a "capital asset" within the meaning of Section 1221 of the Internal Revenue
Code of 1986, as amended (the "Code"). Special tax consequences may be
applicable to particular classes of taxpayers, such as financial institutions,
insurance companies, tax-exempt organizations, broker-dealers, traders in
securities that elect to apply a mark-to-market method of accounting, persons
that hold Suburban Bancshares common stock as part of a hedge, straddle or
conversion transaction, persons who are not citizens or residents of the United
States and stockholders who acquired their shares of Suburban Bancshares common
stock through the exercise of an employee stock option or otherwise as
compensation. The following represents general information only and is based
upon the Code, its legislative history, existing and proposed regulations
thereunder, published rulings and decisions, all as currently in effect as of
the date hereof, and all of which are subject to change, possibly with
retroactive effect. Tax considerations under state, local and foreign laws are
not addressed in this proxy statement/prospectus. All stockholders should
consult with their own tax advisors as to the particular tax consequences of the
merger to them, including the applicability and effect of the alternative
minimum tax and any state, local or foreign income and other tax laws and of
changes in those tax laws.

     Tax Consequences of the Merger Generally.  Neither Columbia Bancorp nor
Suburban Bancshares will be obligated to complete the merger unless they receive
an opinion of Columbia Bancorp's counsel, Piper Marbury Rudnick & Wolfe LLP,
dated the closing date of the merger, to the effect that, on the basis of facts,
representations and assumptions set forth in that opinion, the merger will be
treated as a reorganization within the meaning of Section 368(a) of the Code and
that Columbia Bancorp and Suburban Bancshares will each be a party to the
reorganization under 368(b) of the Code.  This tax opinion will not be binding
on the Internal Revenue Service and neither Columbia Bancorp nor Suburban
Bancshares intends to request any ruling from the Internal Revenue Service as to
the U.S. federal income tax consequences of the merger.

     The above opinion of counsel, which will be delivered on the effective
date, is filed as an exhibit to the registration statement.  Piper Marbury
Rudnick & Wolfe LLP will deliver their opinion on the basis of facts,
representations and assumptions set forth in their opinion that are consistent
with the state of facts expected to exist at the effective time of the merger.
In rendering its opinion, Piper Marbury Rudnick & Wolfe LLP has required and
relied upon certain representations contained in certificates of officers of
Columbia Bancorp and Suburban Bancshares. Based on this opinion, for U.S.
federal income tax purposes (1) no gain or loss will be recognized by Columbia
Bancorp or Suburban Bancshares pursuant to the merger and (2) a stockholder of
Suburban Bancshares who receives solely Columbia Bancorp common stock in
exchange for its shares of Suburban Bancshares common stock in the merger will
not recognize any gain or loss (except, as discussed below, with respect to cash
received instead of fractional shares or dissenters shares of Columbia Bancorp
common stock).

                                      -57-
<PAGE>

     Exchange of Suburban Bancshares Common Stock Solely for Columbia Bancorp
Common Stock.  A stockholder of Suburban Bancshares who receives solely Columbia
Bancorp common stock in exchange for its shares of Suburban Bancshares common
stock in the merger generally will not recognize any gain or loss upon the
exchange. The stockholder may recognize gain or loss, however, with respect to
cash received instead of a fractional share of Suburban Bancshares common stock,
as discussed below. The aggregate adjusted tax basis of the shares of Columbia
Bancorp common stock received in the exchange (including fractional shares
deemed received and redeemed as described below) will be equal to the aggregate
adjusted tax basis of the shares surrendered, and the holding period of the
Columbia Bancorp common stock (including fractional shares deemed received and
redeemed as described below) will include the holding period of the shares of
Suburban Bancshares common stock surrendered.

     Cash Received Instead of a Fractional Interest of Columbia Bancorp Common
Stock.  A stockholder of Suburban Bancshares who receives cash instead of a
fractional share of Columbia Bancorp common stock will be treated as having
received the fractional share pursuant to the merger and then as having
exchanged the fractional share for cash in a redemption by Columbia Bancorp
subject to Section 302 of the Code. This deemed redemption will be treated as a
sale of the fractional share, provided that it is not "essentially equivalent to
a dividend" or is "substantially disproportionate" with respect to the Suburban
Bancshares stockholder. If the deemed redemption is treated as a sale of a
fractional share, a Suburban Bancshares stockholder will recognize capital gain
or loss equal to the difference between the amount of cash received and the
portion of the basis of the shares of Columbia Bancorp common stock allocable to
the fractional interest. This capital gain or loss will be long-term capital
gain or loss if, as of the date of the exchange, the holding period for the
shares is greater than one year.

     Backup Withholding and Information Reporting.  Payments of cash to a holder
surrendering shares of Suburban Bancshares common stock will be subject to
information reporting and "backup" withholding at a rate of 31% of the cash
payable to the holder, unless the holder furnishes its taxpayer identification
number in the manner prescribed in applicable Treasury Regulations, certifies
that number is correct, certifies as to no loss of exemption from backup
withholding and meets certain other conditions. Any amounts withheld from
payments to a holder under the backup withholding rules will be allowed as a
refund or credit against the holder's U.S. federal income tax liability,
provided the required information is furnished to the Internal Revenue Service.

     Tax Consequences to Dissenting Stockholders.  If a Suburban Bancshares
stockholder dissents to the merger and receives solely cash in exchange for its
shares of Suburban Bancshares common stock, the cash received will be treated as
having been received by them as a distribution in redemption of its shares of
Suburban Bancshares common stock, subject to the provisions and limitations of
Section 302 of the Code. See "--Appraisal Rights." Unless the redemption is
treated as a dividend under Section 302(d) of the Code, a stockholder will
recognize gain or loss measured by the difference between the amount of cash
received and the tax basis of the shares of Suburban Bancshares common stock
redeemed. This gain or loss will be capital gain or loss if the shares of
Suburban Bancshares common stock was held by the stockholder as a capital asset
at the time of the merger. If, on the other hand, the redemption is treated as a
dividend under Section 302(d) of the Code, the full amount of cash received by
the stockholder will be treated as ordinary income to the extent of Suburban
Bancshares's current or accumulated earnings and profits.

                                      -58-
<PAGE>

     Under the tests of Section 302 of the Code, the redemption of a dissenting
Suburban Bancshares stockholder's Suburban Bancshares common stock generally
will be treated as a dividend unless the redemption (i) results in a "complete
termination" of the stockholder's direct or indirect stock interest in Columbia
Bancorp under Section 302(b)(3) of the Code, (ii) is "substantially
disproportionate" with respect to the stockholder under Section 302(b)(2) of the
Code or (iii) is "not essentially equivalent to a dividend" with respect to the
stockholder under Section 302(b)(1) of the Code.

     In order to determine whether there has been a complete termination, a
substantially disproportionate redemption or a redemption not essentially
equivalent to a dividend with respect to a dissenting Suburban Bancshares
stockholder, it is necessary to consider the common stock owned by persons from
whom ownership is attributed to such stockholder under the rules of Section 318
of the Code. Under Section 318 of the Code, a stockholder is considered to own
shares that are directly or indirectly owned by certain members of their family
or by certain trusts, partnerships or corporations in which they have an
ownership or beneficial interest. A stockholder is also considered to own any
shares underlying exercisable options he holds. In some cases, a dissenting
Suburban Bancshares stockholder may be deemed to own constructively common stock
held by persons who do not exercise appraisal rights.

Regulatory Approvals Required

     We have agreed to use each of our reasonable best efforts to obtain all
regulatory approvals required to consummate the transactions contemplated by the
merger agreement, which include approval from the FDIC, the Board of Governors
of the Federal Reserve System and state and other regulatory authorities, and
will have completed the filing of these applications and notifications prior to
the date of this proxy statement/prospectus. The merger and the bank merger
cannot proceed in the absence of these regulatory approvals. We cannot assure
you that we will obtain these regulatory approvals, and, if we are able to
obtain them, we cannot assure you when we will receive these approvals or that
there will not be litigation challenging these approvals. Likewise we cannot
assure you that the United States Department of Justice or any state attorney
general will not attempt to challenge the merger or bank merger on antitrust
grounds, or, if such a challenge is made, we cannot assure you as to its result.

     We are not aware of any other material governmental approvals or actions
that are required prior to the parties' consummation of the merger other than
those described below. We presently contemplate that if any additional
governmental approvals or actions are required, we will seek such approvals or
actions. We cannot assure you, however, that we will be able to obtain any of
these additional approvals or actions.

     Federal Deposit Insurance Corporation.  The acquisition of Suburban
Bancshares as contemplated in this proxy statement/prospectus is subject to
approval of the FDIC pursuant to the Bank Merger Act (12 U.S.C. Sec. 1828 et
seq.) ("BMA"). The BMA requires that the FDIC consider, among other factors, the
financial and managerial resources and future prospects of the existing and
proposed organizations and the convenience and needs of the communities to be
served. In considering financial and managerial factors, the FDIC will evaluate,
among other things, the adequacy of the capital of the parties to the
transaction. In addition, the FDIC will assess the degree to which the parties
are taking appropriate steps to assure that their electronic data processing
systems and those of their vendors are Year 2000 compliant and their plans for
ensuring Year 2000 readiness of the resulting organization.

                                      -59-
<PAGE>

     The FDIC is prohibited from approving any transaction if it would result in
a monopoly or would be in furtherance of any combination or conspiracy to
monopolize or to attempt to monopolize the business of banking in any part of
the United States or if its effect in any section of the United States would be
substantially to lessen competition, or to tend to create a monopoly, or result
in a restraint of trade, unless the FDIC finds that the anti-competitive effects
of the transaction are clearly outweighed in the public interest by the probable
effect of the transaction in meeting the convenience and needs of the
communities to be served.

     In addition, the FDIC must take into account the record of performance of
the existing and proposed institutions under the Community Reinvestment Act of
1977 in meeting the credit needs of the entire community, including low- and
moderate-income neighborhoods, served by such institutions. Applicable
regulations also require publication of notice of the application for approval
of the acquisition and provide an opportunity for the public to comment on the
application in writing and to request a hearing. Subject to certain exceptions,
the BMA provides that no bank merger may be completed until the 15th day after
approval, during which time the United States Department of Justice may
challenge the Reorganization Agreement on antitrust grounds. Columbia Bancorp
will submit an application to the FDIC for approval to complete the merger.

     Federal Reserve Board.  In view of the FDIC's consideration under the BMA
of the bank merger, which will occur contemporaneously with the merger, the
Federal Reserve Board may waive application requirements for prior approval of
the merger under the Bank Holding Company Act and the Federal Reserve Board's
Regulation Y. Columbia Bancorp will request such a waiver from the Federal
Reserve Board.

     Suburban Bancshares' and Columbia Bancorp's rights to exercise their
respective options under the option agreements also require the prior approval
of the Federal Reserve Board, to the extent that the exercise of their options
under the option agreements would cause Suburban Bancshares or Columbia Bancorp
to own more than 5% of the outstanding shares of the other. Each of Columbia
Bancorp and Suburban Bancshares intends to file the required application and
notifications with the Federal Reserve Board for approval of the exercise of its
option under the relevant Option Agreement prior to any exercise of any option
under the relevant Option Agreement. In considering whether to approve Suburban
Bancshares' or Columbia Bancorp's right to exercise its respective option, the
Federal Reserve Board would generally apply the same statutory criteria it would
apply to its consideration of approval of the merger.

     State Regulatory Authorities.  The merger and the bank merger are also
subject to the approval the Maryland Commissioner of Financial Regulation.

Nasdaq Stock Market Listing

     It is a condition to the merger that any shares of Columbia Bancorp common
stock issuable in the merger be authorized for listing on The Nasdaq Stock
Market, subject to official notice of issuance.

Appraisal Rights

     Columbia Bancorp stockholders do not have dissenters' appraisal rights in
connection with the merger.

                                      -60-
<PAGE>

     If the merger is completed, Suburban Bancshares stockholders who do not
vote for the adoption of the merger agreement and who otherwise comply with the
provisions of Section 262 of the Delaware General Corporation Law summarized
below will be entitled to an appraisal by the Delaware Court of Chancery of the
"fair value" of their shares of Suburban Bancshares common stock. Columbia
Bancorp has the right to terminate the merger agreement and be released from all
obligations if, immediately prior to the effective date, the number of Suburban
Bancshares stockholders who have demanded appraisal rights and not withdrawn
those demands jeopardizes the qualification of the merger for pooling-of-
interests accounting treatment and KPMG LLP fails or refuses to deliver a letter
to Columbia Bancorp to that effect.

     To perfect their appraisal rights, Suburban Bancshares stockholders must
strictly comply with the procedures in Section 262. Failure to strictly comply
with these procedures will result in the loss of appraisal rights. Holders of
options to acquire shares of Suburban Bancshares common stock will not be
entitled to appraisal rights with respect their options.

     THE FOLLOWING IS A SUMMARY OF THE MATERIAL ASPECTS OF SECTION 262. THE FULL
TEXT OF SECTION 262 IS REPRINTED AS APPENDIX H TO THIS JOINT/PROXY STATEMENT
PROSPECTUS. YOU SHOULD READ APPENDIX H IN ITS ENTIRETY.

     To perfect appraisal rights under Section 262 with respect to his or her
shares of Suburban Bancshares common stock, a Suburban Bancshares stockholder:

     .    must not vote for the adoption of the merger agreement; and

     .    must deliver to Suburban Bancshares a written demand for appraisal of
          his shares of Suburban Bancshares common stock before the vote on the
          proposal to adopt the merger agreement.

     In order not to vote in favor of the adoption of the merger agreement, a
Suburban Bancshares stockholder must either:

     .    not return a proxy card and not vote in person in favor of the
          adoption of the merger agreement;

     .    return a proxy card with the "Against" or "Abstain" box checked;

     .    vote in person against the adoption of the merger agreement; or

     .    register in person an abstention from the proposal to adopt the merger
          agreement.

     A written demand for appraisal must reasonably inform Suburban Bancshares
of the identity of the Suburban Bancshares stockholder and his or her intent to
demand appraisal of his or her shares of Suburban Bancshares common stock. This
written demand for appraisal must be separate from any proxy or vote in person
against or abstaining from the adoption of the merger agreement. A proxy or vote
in person against the adoption of the merger agreement will not, in and of
itself, constitute a demand for appraisal.

                                      -61-
<PAGE>

     A Suburban Bancshares stockholder wishing to assert appraisal rights must
be the record holder of his or her shares of Suburban Bancshares common stock on
the date the written demand for appraisal is made. Only a holder of record of
shares of Suburban Bancshares common stock is entitled to assert appraisal
rights for the shares of Suburban Bancshares common stock registered in that
holder's name. Moreover, to preserve his or her appraisal rights, a Suburban
Bancshares stockholder must continue to hold his or her shares through the
effective time. Accordingly, a Suburban Bancshares stockholder who is the record
holder of shares of Suburban Bancshares common stock on the date the written
demand for appraisal is made, but who subsequently transfers shares prior to the
effective time, will lose any right to appraisal in respect of those shares.

       ALL WRITTEN DEMANDS FOR APPRAISAL MUST BE MAILED OR DELIVERED TO:
                           SUBURBAN BANCSHARES, INC.
                          7505 GREENWAY CENTER DRIVE
                           GREENBELT, MARYLAND 20768
                        ATTENTION: CORPORATE SECRETARY

  OR SHOULD BE DELIVERED TO THE SECRETARY AT THE SUBURBAN BANCSHARES SPECIAL
              MEETING PRIOR TO THE VOTE ON THE MERGER AGREEMENT.

     Within ten days after the effective date, Columbia Bancorp, as successor to
Suburban Bancshares, will notify each Suburban Bancshares stockholder who
properly delivered to Suburban Bancshares a written demand for appraisal and has
not voted for the adoption of the merger agreement, of the effective time.

     Within 120 days after the effective date, any Suburban Bancshares
stockholder who has complied with the provisions will be entitled, within ten
days after written request, to receive from Columbia Bancorp, as successor to
Suburban Bancshares, a statement of the aggregate number of shares of Suburban
Bancshares common stock not voted in favor of the adoption of the merger
agreement and with respect to which demands for appraisal were received, and the
number of holders of those shares.

     Within 120 days after the effective date, Columbia Bancorp, as successor to
Suburban Bancshares, or any Suburban Bancshares stockholder who has complied
with the above requirements may file a petition in the Delaware Court of
Chancery demanding a determination of the fair value of shares of Suburban
Bancshares common stock. If no such petition is filed, appraisal rights will be
lost for all Suburban Bancshares stockholders who had previously demanded
appraisal of their shares. Suburban Bancshares is not under any obligation, and
has no present intention, to file a petition with respect to appraisal of the
value of the shares of Suburban Bancshares common stock.

     Any Suburban Bancshares stockholder who properly demands appraisal of his
or her shares of Suburban Bancshares common stock but fails to perfect, or
effectively withdraws or loses, his or her right to appraisal, will then have
only the right to receive shares of Columbia Bancorp common stock for his or her
shares in accordance with the terms of the merger.

     If a petition for an appraisal is timely filed and a copy served upon
Columbia Bancorp, as successor to Suburban Bancshares, Columbia Bancorp will
then be obligated within 20 days to file with the Delaware Register in Chancery
a list containing the names and addresses of the Suburban Bancshares
stockholders who have demanded appraisal of their shares of Suburban Bancshares
common stock and

                                      -62-
<PAGE>

with whom agreements as to the value of their shares have not been reached.
After notice to the Suburban Bancshares stockholders as required by the Delaware
Court of Chancery, the Delaware Court of Chancery may conduct a hearing on such
petition to determine those Suburban Bancshares stockholders entitled to
appraisal rights. The Delaware Court of Chancery may require the Suburban
Bancshares stockholders who demanded appraisal rights of their shares of
Suburban Bancshares common stock to submit their stock certificates to the
Delaware Register in Chancery for notation of the pendency of the appraisal
proceeding. If any Suburban Bancshares stockholder fails to comply, the Delaware
Court of Chancery may dismiss the proceedings as to that Suburban Bancshares
stockholder.

     After determining which Suburban Bancshares stockholders are entitled to
appraisal, the Delaware Court of Chancery will appraise the "fair value" of
their shares of Suburban Bancshares common stock, excluding any element of value
arising from the accomplishment or expectation of the merger, together with a
fair rate of interest, if any, to be paid upon the amount determined to be the
fair value. Suburban Bancshares stockholders considering seeking appraisal
should be aware that the fair value of their shares as determined under Section
262 could be more than, the same as or less than the consideration they are
entitled to receive under the terms of the merger if they did not seek appraisal
of their shares of Suburban Bancshares common stock, and that investment banking
opinions as to fairness from a financial point of view are not necessarily
opinions as to fair value under Section 262.

     The costs of an appraisal action may be determined by the Delaware Court of
Chancery and charged to the parties as the Delaware Court of Chancery deems
equitable. The Delaware Court of Chancery may also order that all or a portion
of the expenses incurred by any Suburban Bancshares stockholder in connection
with an appraisal be charged pro rata against the value of all of the shares
entitled to appraisal. In the absence of such determination or assessment, each
party bears its own expenses.

     At any time within 60 days after the effective time, any Suburban
Bancshares stockholder will have the right to withdraw his or her demand for
appraisal and to accept shares of Columbia Bancorp common stock for shares of
Suburban Bancshares common stock in accordance with the terms of the merger.
After this period, a Suburban Bancshares stockholder may withdraw his or her
demand for appraisal only with the written consent of Suburban Bancshares. No
petition timely filed in the Delaware Court of Chancery demanding appraisal will
be dismissed as to any Suburban Bancshares stockholder without the approval of
the Delaware Court of Chancery, which may be conditioned on terms the Delaware
Court of Chancery deems just.

     Any Suburban Bancshares stockholder who has demanded and perfected an
appraisal in compliance with Section 262 will not, after the effective time of
the merger, be entitled to vote his or her shares for any purpose or be entitled
to the payment of dividends, except dividends payable to Suburban Bancshares
stockholders prior to the effective time.

Resale of Columbia Bancorp Common Shares After the Merger

     Columbia Bancorp common stock issued pursuant to the merger will not be
subject to any restrictions on transfer arising under the Securities Act of
1933, as amended (the "Securities Act"), except for shares issued to any
Suburban Bancshares stockholder who may be deemed to be an "affiliate" of
Suburban Bancshares for purposes of Rule 145 under the Securities Act.

     This proxy statement/prospectus does not cover resales of shares of
Columbia Bancorp common stock received by any person who may be deemed to be
such an affiliate.


                                      -63-
<PAGE>

     Persons who may be deemed to be affiliates of Suburban Bancshares generally
include individuals or entities that control, are controlled by, or are under
common control with Suburban Bancshares, and generally include the executive
officers and directors of Suburban Bancshares and entities controlled by
directors of Suburban Bancshares. Affiliates may not sell their shares of
Columbia Bancorp common stock acquired in connection with the merger, except
pursuant to an effective registration under the Securities Act covering such
shares or in compliance with Rule 145 under the Securities Act (or Rule 144
under the Securities Act in the case of persons who become affiliates of
Columbia Bancorp) or another applicable exemption from the registration
requirements of the Securities Act. In general, Rule 145 under the Securities
Act provides that, for one year following the effective time of the merger, an
affiliate (together with certain related persons) would be entitled to sell
shares of Columbia Bancorp common stock acquired in connection with the merger
only through unsolicited "broker transactions" or in transactions directly with
a "market maker," as such terms are defined in Rule 144 under the Securities
Act. Additionally, the number of shares to be sold by an affiliate (together
with certain related persons and certain persons acting in concert) within any
three-month period for purposes of Rule 145 under the Securities Act may not
exceed the greater of 1% of the outstanding shares of Columbia Bancorp common
stock or the average weekly trading volume of such shares during the four
calendar weeks preceding such sale (excluding such persons trading). Rule 145
under the Securities Act will remain available to affiliates if Columbia Bancorp
timely files reports under the Exchange Act with the SEC. One year after the
effective time of the merger, an affiliate will be able to sell such shares of
Columbia Bancorp common stock without being subject to such manner of sale or
volume limitations, provided that Columbia Bancorp is current with its Exchange
Act informational filings and such affiliate is not then an affiliate of
Columbia Bancorp. Two years after the effective time of the merger, an affiliate
will be able to sell such shares of Columbia Bancorp common stock without any
restrictions so long as such affiliate had not been an affiliate of Columbia
Bancorp for at least three months prior to the date of such sale.

                                      -64-
<PAGE>

                             THE MERGER AGREEMENT

     The following is a summary of certain provisions of the merger agreement.
This summary is qualified in its entirety by reference to the merger agreement,
which is incorporated by reference in its entirety and attached to this proxy
statement/prospectus as Appendix A. Columbia Bancorp and Suburban Bancshares
stockholders are urged to read the merger agreement in its entirety for a more
complete description of the merger.

General

     Pursuant to the merger agreement, as amended, Suburban Bancshares will
merge with and into Columbia Bancorp, with Columbia Bancorp surviving the
merger. The stockholders of Suburban Bancshares will receive the consideration
described below. The effective date of the merger will occur following the
satisfaction or waiver, where permissible, of all conditions to completion of
the merger specified in the merger agreement. Columbia Bancorp and Suburban
Bancshares may also mutually agree on a different date. We expect that the
effective date of the merger will occur on _____________, 2000.

     As part of the merger, Columbia Bancorp and Suburban Bancshares will cause
Columbia Bank and Suburban Bank to enter into a bank plan of merger.  The bank
plan of merger provides that Suburban Bank will merge with and into Columbia
Bank, with Columbia Bank surviving. We expect to complete the bank merger
concurrently with completion of the merger.

     On or prior to the effective date of the merger, we will file articles of
merger with the Maryland State Department of Assessments and Taxation and a
certificate of merger with the Delaware Secretary of State, and each such
document will set forth the effective date of the merger.  Either Columbia
Bancorp or Suburban Bancshares can terminate the merger agreement if, among
other reasons, the merger does not occur on or before June 30, 2000 and the
terminating party has not breached or failed to perform any of its obligations
under the merger agreement. See "-- Termination; Effect of Termination" on page
73.

Conversion Ratios; Fractional Shares

     At the time the merger becomes effective, each share of issued and
outstanding Suburban Bancshares common stock, except for shares of dissenting
stockholders, will be canceled and cease to be outstanding and will be exchanged
for shares of Columbia Bancorp common stock equivalent to an average market
value of $3.00 per share.  The conversion ratio necessary to cause the average
market value of shares of Columbia Bancorp common stock exchanged for each share
of Suburban Bancshares common stock to be $3.00 per share will continually
change until the merger is completed, except that the conversion ratio will not
be above 0.2338 nor below 0.2196. No fractional shares will be issued.  Instead,
stockholders will be paid in cash the amount equal to the fractional share
multiplied by the average daily high and low trade prices per share of Columbia
Bancorp common stock for the 10 trading days ending three trading days before
the effective date.

Certain Representations and Warranties

     The merger agreement contains various representations and warranties made
by Columbia Bancorp and Suburban Bancshares, some of which are qualified as to
materiality, regarding the following matters, among others:

                                      -65-
<PAGE>

  .  corporate existence, organization, standing, authority and capitalization;

  .  ownership of the shares of capital stock of its subsidiaries, and the
     corporate existence, organization, standing and authority of its
     subsidiaries;

  .  that the merger agreement and the related transactions will not result in a
     violation of Columbia Bancorp's or Suburban Bancshares' organizational
     documents or contracts to which Columbia Bancorp or Suburban Bancshares, or
     any of their subsidiaries, is a party, or violate any law, rule or
     regulation;

  .  consistency of financial statements with generally accepted accounting
     principles;

  .  the filing of tax returns and payment of taxes;

  .  absences of undisclosed liabilities;

  .  absence of certain material adverse events, changes or effects;

  .  accuracy of information supplied by Columbia Bancorp and Suburban
     Bancshares in connection with the merger agreement and related documents;

  .  quality of title to properties and assets;

  .  material contracts;

  .  absence of pending or threatened suits, actions or other proceedings;

  .  absence of material environmental violations, actions or liabilities;

  .  labor matters;

  .  retirement and other employee plans and matters relating to the Employee
     Retirement Income Security Act of 1974;

  .  transactions with affiliates;

  .  consents and regulatory approvals necessary to complete the merger;

  .  compliance with laws and required licenses and permits;

  .  corporate power and authority to execute, deliver and perform its
     obligations under the merger agreement, and to consummate the merger,
     subject only to stockholder approval;

  .  maintenance of adequate insurance and financial institutions bonds;

                                      -66-
<PAGE>

  .  no claims for brokerage commissions or advisory fees, except to the
     financial advisors of Columbia Bancorp and Suburban Bancshares in
     connection with the merger; and

  .  year 2000 compliance.

     The representations and warranties of Suburban Bancshares and Columbia
Bancorp will not be deemed waived or otherwise affected by any investigation
made by any party and do not survive beyond the effective time of the merger.

Certain Covenants and Agreements

     Conduct of Business Pending Merger.  Pursuant to the merger agreement,
Suburban Bancshares and Columbia Bancorp have each agreed (except as permitted
by the other party or as otherwise expressly contemplated by the merger
agreement) to conduct their respective businesses in the ordinary course
consistent with past practice and that, pending the merger, they will not, nor
will they permit any of their subsidiaries to:

  .  amend their respective charters or bylaws or comparable documents of any
     subsidiary;

  .  change their authorized, issued or outstanding capital stock, except for
     outstanding stock options which are currently exercisable;

  .  declare any cash dividend on its capital stock, except that Columbia
     Bancorp may declare a dividend that does not exceed $0.10 per share;

  .  increase the compensation or benefits of any employees, outside the
     ordinary course of its business and consistent with past practices or enter
     into or modify any employment contract with any of its officers or
     employees;

  .  make any change in any of their accounting policies or practices or take
     any action that would prevent Columbia Bancorp from accounting for the
     merger as a pooling-of-interests;

  .  incur any liability for borrowed money except extensions of credit other
     than in the ordinary course of business, provided the extensions of credit
     are at a variable rate with maturities of one year or less;

  .  enter into any material contract, commitment or transaction outside the
     ordinary course of business and consistent with past practice; or

  .  enter into any contract with respect to the foregoing or authorize any of,
     or commit or agree to take any of, the foregoing actions.

                                      -67-
<PAGE>

     Pending the Effective Date, Columbia Bancorp and Suburban Bancshares have
agreed to:

     .    use commercially reasonable efforts to preserve their business
          organizations and assets and to keep available the services of their
          full-time officers and employees;

     .    continue in effect the present method of conducting their businesses;
          and

     .    consult with the other party as to making decisions or actions in
          matters other than those in the ordinary course of business, or
          involving any capital expenditures in excess of $25,000.

Columbia Bancorp and Suburban Bancshares have jointly agreed:

     .    to submit the merger agreement and related transactions to their
          stockholders for approval;

     .    to use their best efforts to obtain all required regulatory approvals
          and required third party consents;

     .    to deliver to the other copies of all securities documents when filed;

     .    to use their best efforts to prevent their agents and representatives
          from engaging in any merger, acquisition or similar transaction;

     .    to cooperate with each other and use their best efforts to identify
          those persons who may be deemed to be affiliates of Columbia Bancorp
          and Suburban Bancshares;

     .    to take all actions necessary to complete the transactions
          contemplated by the merger agreement;

     .    to use their best efforts not to permit any of their officers,
          directors, employees or other representatives to take any action that
          would prevent Columbia Bancorp from treating the merger as a pooling-
          of-interests for financial reporting purposes;

     .    to file all tax returns and pay all taxes when due; and

     .    to agree upon the form and substance of any press release or public
          disclosure related to the merger.

          No Solicitation. The merger agreement provides that, except to the
extent legally required by the fiduciary obligations of their boards of
directors prior to the effective time of the merger, neither Suburban Bancshares
nor Columbia Bancorp, nor any of their respective subsidiaries will, or will
permit any of their agents or representatives to directly or indirectly, solicit
or initiate any inquiries or the making of any offer or proposal with respect
to:

     .    any merger, consolidation, or other business combination involving
          Suburban Bancshares, Columbia Bancorp or any of their respective
          subsidiaries; or

     .    the acquisition of all or any significant part of the assets or
          capital stock of Suburban Bancshares, Columbia Bancorp or any of their
          respective subsidiaries.

                                      -68-
<PAGE>

     Those Columbia Bancorp and Suburban Bancshares stockholders who are party
to the support agreements have also agreed that, in their capacity as
stockholders, they will not directly or indirectly solicit, initiate or
encourage any inquiries or proposals or participate in any discussions or
negotiations with anyone concerning any merger, acquisition or similar
transaction.

     Composition of the Board of Directors of Columbia Bancorp and Columbia Bank
Following the Merger.  In connection with the merger, Columbia Bancorp has
agreed to increase its board of directors by five members at the effective date
and to cause its board of directors, consistent with their fiduciary duties and
in accordance with Maryland law, to appoint Winfield M. Kelly, Jr., Albert W.
Turner, Lawrence A. Shulman, Vincent D. Palumbo, and Kenneth H. Michael, each of
whom are currently members of Suburban Bancshares' board of directors, to become
members of Columbia Bancorp's board of directors promptly after the effective
time of the merger.  The other 16 directors will be those persons serving as
directors of Columbia Bancorp at the time of the effective date and will
continue to serve in their respective classes.  Also at the effective date, the
board of directors of Columbia Bank will be increased by five members.  All of
the directors of Columbia Bank  immediately prior to the effective date will
continue as directors, and the five directors from Suburban Bancshares mentioned
above will also become directors of Columbia Bank.

Conditions to the Merger

     Our obligation to effect the merger is subject to the satisfaction or
waiver (if permitted by law), at or prior to the merger, of the following
conditions, among others:

     Representations, Warranties and Covenants.  Each of the representations and
warranties of the other party contained in the merger agreement must be true and
correct, as of the date of the merger agreement, and, except to the extent such
representations and warranties speak as of an earlier date, as of the effective
time of the merger as though they were made at the effective time of the merger.
Columbia Bancorp must receive an officers' certificate to that effect.  Suburban
Bancshares will receive a similar certificate signed on Columbia Bancorp's
behalf.  The other party must have performed in all material respects all of its
obligations required to be performed under the merger agreement prior to the
effective time of the merger.  Columbia Bancorp will receive an officers'
certificate to that effect. Suburban Bancshares will receive a similar
certificate signed on Columbia Bancorp's behalf.

     Material Adverse Change.  Any materially adverse change in the condition,
results of operations, assets liabilities or business of the other party and its
subsidiaries cannot have occurred since December 31, 1998.  A material adverse
change will include, without limitation, (i) a reduction of stockholders' equity
to less than $19,366,000 in the case of Suburban Bancshares and $38,000,000 in
the case of Columbia Bancorp, (ii) a decrease in the net income for calendar
year 1999 and through the effective date to less than $625,000 in the case of
Suburban Bancshares and $3,400,000 in the case of Columbia Bancorp, or (iii) an
increase in the ratio of non-performing assets to total assets to above 1.5%.

     Regulatory Approvals.  We must obtain all licenses, permits, consents,
approvals, authorizations, qualifications and orders of governmental authorities
and other third parties that are necessary in connection with the merger as
contemplated by the merger agreement.  These conditions may be waived, except
where failure to obtain them would result in a materially adverse effect on

                                      -69-
<PAGE>

Columbia Bancorp or Suburban Bancshares, or would so materially and adversely
affect the economic or business benefits of the merger that Columbia Bancorp
would not have entered into the proposed merger.

     Stockholder Approval.  Stockholders holding a majority of the issued and
outstanding voting stock of Suburban Bancshares and stockholders holding at
least two-thirds of the issued and outstanding voting stock of Columbia Bancorp
must approve and adopt the merger agreement and approve the merger.  Also, the
sole stockholder of each of Suburban Bank and Columbia Bank must approve the
merger of those two banks as contemplated by the merger agreement.

     Effectiveness of Registration Statement.  The Registration Statement on
Form S-4 (of which this proxy statement/prospectus is a part) must become
effective in accordance with the provisions of the Securities Act.  The SEC must
not have issued any stop order suspending the effectiveness of the Registration
Statement, and the SEC must not have initiated proceedings for that purpose.

     Nasdaq Listing.  The shares of Columbia Bancorp common stock issued in
connection with the merger must be approved for listing on The Nasdaq Stock
Market, subject to official notice of issuance.

     No Injunctions.  No action or proceeding challenging the merger in
connection with the mergers can be threatened or pending.  No order issued by
any governmental entity having jurisdiction over Columbia Bancorp, Suburban
Bancshares, or any of their subsidiaries that materially restricts, prevents or
prohibits the consummation of the merger can be in effect or pending.

     Consents.  Suburban Bancshares and Columbia Bancorp must have obtained the
consent, approval or waiver of each entity whose consent or approval is required
in connection with the transactions contemplated by the merger agreement under
any contract, except where the failure to obtain this consent would not
reasonably be expected, to have a material adverse effect on Suburban
Bancshares, Columbia Bancorp or the combined company.

     Tax Opinion.  Columbia Bancorp and Suburban Bancshares must have received
an opinion from Columbia Bancorp's tax counsel that, among other things, the
merger will qualify for United States federal income tax purposes as a tax-free
reorganization.

     Fairness Opinion.  Each of Columbia Bancorp and Suburban Bancshares have
received an opinion from its financial advisor that the issuance of shares of
Columbia Bancorp common stock in the merger will be fair from a financial point
of view to the Columbia Bancorp stockholders or the Suburban Bancshares
stockholders, as the case may be.

     Legal Opinions.  Counsel for Columbia Bancorp and Suburban Bancshares must
have delivered certain legal opinions regarding each of their authorizations to
execute the merger agreement and other documents.

     Pooling Letter.  Columbia Bancorp must have received a letter from KPMG LLP
stating that the mergers will qualify for pooling-of-interests accounting
specified in Accounting Principles Board Opinion No. 16 if the mergers are
completed according to the merger agreement. In rendering this letter, KPMG LLP
requires delivery of and will rely upon certain representation letters delivered
by Columbia Bancorp and Suburban Bancshares and a pooling letter delivered by
Stegman & Company.

                                      -70-
<PAGE>

     At any time prior to the effective time of the merger, each of Columbia
Bancorp and Suburban Bancshares may waive the compliance with any conditions
that may legally be waived. However, we may not waive conditions that are
required by law to complete the merger, including (i) the requirement for
stockholder approval, (ii) the requirement for regulatory approvals, and (iii)
the requirement that the registration statement be effective on the closing
date.  Furthermore, after approval of the merger agreement by the stockholders
of Suburban Bancshares and Columbia Bancorp, we cannot waive any conditions that
under applicable law would require further approval of our stockholders without
obtaining stockholder approval. See "-- Waiver."

Termination

     We may terminate the merger agreement at any time prior to the completion
of the merger, by mutual written consent.

     Either Columbia Bancorp or Suburban Bancshares may terminate the merger
agreement at any time prior to the completion of the merger:

     .    if the merger has not been completed by June 30, 2000, unless the
          failure to complete the merger is the result of a breach of the merger
          agreement by the party seeking to terminate the merger agreement, or

     .    if prior to June 30, 2000 any court has entered an order which
          prohibits completion of the mergers and the transactions contemplated
          by the merger agreement.

     Columbia Bancorp may terminate the merger agreement at any time prior to
the completion of the merger:

     .    if there has been a material breach of any of the representations or
          warranties, covenants or agreements of Suburban Bancshares in the
          merger agreement, which is not curable within 60 days after Columbia
          Bancorp gives written notice of the breach to Suburban Bancshares;

     .    if Columbia Bancorp does not obtain stockholder approval, unless the
          failure to obtain stockholder approval is due to the failure of
          Columbia Bancorp to perform or observe the agreements set forth in the
          merger agreement;

     .    if any permanent injunction, order, decree or ruling by any
          governmental entity preventing the completion of the merger has become
          final and non-appealable;

     .    if prior to June 30, 2000 any action or proceeding against Columbia
          Bancorp or against Suburban Bancshares or any of their respective
          subsidiaries is pending which seeks to prevent completion of the
          transactions contemplated by the merger agreement; or

     .    if prior to June 30, 2000, any approval, consent, or waiver of any
          governmental entity have been denied which are required to permit the
          completion of the transactions contemplated by the merger agreement;

     .    if prior to June 30, 2000 any approval, consent, or waiver of any
          governmental entity required to permit completion of the transactions
          contemplated by the merger agreement

                                      -71-
<PAGE>

          include any condition or requirement that would (i) have a material
          adverse effect on Columbia Bancorp or Suburban Bancshares, or (ii) so
          materially and adversely affect the economic or business benefits of
          the mergers that Columbia Bancorp would not have entered into the
          merger agreement if it had known of these conditions or requirements;

     .    if, immediately prior to the effective date, the number of Suburban
          Bancshares stockholders who have demanded appraisal rights and not
          withdrawn those demands jeopardizes the qualification of the merger
          for pooling-of-interests accounting treatment and KPMG LLP fails or
          refuses to deliver a letter to Columbia Bancorp to that effect; or

     .    if Columbia Bancorp's board of directors vote to negotiate the sale of
          Columbia Bancorp to another party.

     Suburban Bancshares may terminate the merger agreement at any time prior to
the completion of the merger:

     .    if there has been a breach of any of the representations or
          warranties, covenants or agreements of Columbia Bancorp in the merger
          agreement, which is not curable within 60 days after written notice of
          this breach is given by Suburban Bancshares to Columbia Bancorp,

     .    if Suburban Bancshares' board of directors votes to negotiate the sale
          of Suburban Bancshares to another party; or

     .    if Suburban Bancshares does not obtain stockholder approval, unless
          the failure to obtain stockholder approval is due to the failure of
          Suburban Bancshares to perform or observe the agreements set forth in
          the merger agreement.

Amendment; Waiver

     Subject to applicable legal restrictions, at any time prior to the
completion of the merger, the parties may:


     .    amend the merger agreement;

     .    extend the time for the performance of any of the obligations or other
          acts of the other party required in the merger agreement;

     .    waive any inaccuracies in the representations and warranties of the
          other party contained in the merger agreement; or

     .    waive compliance by the other party with any of the agreements or
          conditions contained in the merger agreement, except for the
          requirements of stockholder approval, regulatory approval and the
          absence of any order, decree or injunction preventing the merger.

     We amended the merger agreement on November 24, 1999 to provide for the
effects of dissenting stockholders. After you have approved the merger
agreement, however, we cannot modify

                                      -72-
<PAGE>

either the amount or the form of consideration you will receive upon the
completion of the merger or otherwise materially adversely affect you without
stockholder approval.

Expenses

     We will each pay all of our respective costs and expenses, including fees
and expenses of financial consultants, accountants and legal counsel, except
that:


     .    we will equally share the cost of filing fees in respect of bank
          regulatory approvals required in order to complete the mergers;

     .    Columbia Bancorp will pay the registration fee of the SEC;

     .    Columbia Bancorp will pay the fee payable to The National Association
          of Securities Dealers, Inc. in respect of the listing on The Nasdaq
          Stock Market of the shares of Columbia Bancorp common stock to be
          issued in the merger; and

     .    Columbia Bancorp will pay the costs of printing and mailing the proxy
          statement/prospectus.

                                      -73-
<PAGE>

                            STOCK OPTION AGREEMENTS

     The following description sets forth the material provisions of each of the
Columbia Bancorp stock option agreement and the Suburban Bancshares stock option
agreement, but is not complete and is subject to the full texts of, and
qualified in its entirety by reference to, these agreements, which are attached
as Appendices D and E, respectively, to this proxy statement/prospectus and are
incorporated herein by reference. All Columbia Bancorp stockholders and Suburban
Bancshares stockholders are urged to read each of the Columbia Bancorp stock
option agreement and the Suburban Bancshares stock option agreement carefully
and in its entirety.


General

     As an inducement for Columbia Bancorp to enter into the merger agreement,
we entered into the Suburban Bancshares stock option agreement pursuant to which
Suburban Bancshares granted Columbia Bancorp an option to purchase shares of
Suburban Bancshares common stock. As an inducement for Suburban Bancshares to
enter into the merger agreement, we also entered into the Columbia Bancorp stock
option agreement pursuant to which Columbia Bancorp granted Suburban Bancshares
an option to purchase shares of Columbia Bancorp common stock. Except as
otherwise noted below, the terms and conditions of the Columbia Bancorp stock
option agreement and the Suburban Bancshares stock option agreement are
identical in all material respects.


Exercise; Expiration

     Columbia Bancorp granted Suburban Bancshares an option to purchase up to
497,140 shares of Columbia Bancorp common stock, and Suburban Bancshares granted
Columbia Bancorp an option to purchase up to 2,807,668 shares of Suburban
Bancshares common stock. Although these numbers are subject to adjustment in
certain cases, as described below, they will never exceed 19.9% of the number of
shares of Suburban Bancshares common stock or 9.9% of Columbia Bancorp common
stock, as the case may be, outstanding immediately before exercise of the
option. The exercise price of the Columbia Bancorp option is $13.063 per share
of Columbia Bancorp common stock and the exercise price of the Suburban
Bancshares option is $2.313 per share of Suburban Bancshares common stock, but
each per share option price is subject to adjustment in certain cases (this
exercise price, as adjusted, is referred to below as the "option price").

     Each of Columbia Bancorp and Suburban Bancshares can exercise its option
if a "purchase event" occurs prior to completion of the merger or the
termination of the merger agreement according to its terms. The purchase of any
shares of Columbia Bancorp and Suburban Bancshares common stock pursuant to the
options is subject to compliance with applicable law.

     The option agreements generally define the term "purchase event" to mean
any of the following events or transactions:

     .    the issuer of the option or one of its significant subsidiaries,
          without the prior written consent of the grantee of the option, enters
          into an agreement to engage in a merger, sale or similar transaction
          with a third party;

                                      -74-
<PAGE>

     .    a third party acquires beneficial ownership or the right to acquire
          beneficial ownership of 15% or more of the outstanding shares of the
          issuer of the option's common stock;

     .    a third party has made a bona fide proposal to the issuer of the
          option or its stockholders to engage in merger, sale or similar
          transaction and this proposal has been publicly announced and after
          the announcement the stockholders fail to vote to approve the merger;
          or

     .    the issuer of the option willingly breaches any covenant or
          obligation contained in the merger agreement after a third party has
          proposed a merger, sale or similar transaction, and following the
          breach the grantee of the option is entitled to terminate the merger
          agreement.

     The stock option agreements terminate upon any of the following: (i)
completion of the merger; (ii) termination of the merger agreement in accordance
with its terms provided that this would not include a termination of the merger
agreement by the grantee of the option based on a willful breach of a
representation, warranty, covenant or other agreement contained in the merger
agreement; or (iii) the passage of 12 months, subject to extension in order to
obtain required regulatory approvals, after termination of the merger agreement
by the grantee of the option based on a willful breach by the issuer of the
option of a representation warranty, covenant or other agreement contained in
the merger agreement.

     If the option becomes exercisable, it may be exercised in whole or in part
within sixty days following the notice of exercise. The times during which the
grantee has the right to exercise the option and certain other rights under the
stock option agreement are subject to an extension in order to obtain required
regulatory approvals and comply with applicable regulatory waiting periods. The
option price and the number of shares issuable under the option are subject to
adjustment in the event of specified changes in the capital stock of the issuer
of the option.

Registration Rights

     In connection with the stock option agreements, the issuer of the option
agreed to file one registration statement for the shares received upon exercise
of the option in order to permit the sale of these shares.  The issuer of the
option must use its best efforts to cause the registration statement to become
effective and remain effective for at least 270 days.

                                      -75-
<PAGE>

Purpose of the Agreements

     Arrangements such as the stock option agreements are customarily entered
into in connection with announced mergers involving publicly traded companies to
increase the likelihood that the transactions will be consummated in accordance
with their terms, and to compensate the person granted the option for the
efforts undertaken and the expenses and losses incurred by the person if the
transaction is not completed. The stock option agreements may have the effect of
discouraging offers by third parties to acquire the issuer of the option, even
if those persons were prepared to offer to pay consideration to the issuer of
the option's stockholders that has a higher current market price than the shares
of the grantee of the option common stock to be received by the holders pursuant
to the merger agreement. Also, following consultation with our respective
independent accountants, we believe that the exercise of either of the stock
options is likely to prohibit another acquiror from accounting for any
acquisition of the issuer of the stock option using the "pooling of interests"
accounting method for a period of two years.

     To our best knowledge no event giving rise to the right to exercise either
option has occurred as of the date of this proxy statement/prospectus.


                              SUPPORT AGREEMENTS

     Concurrently with the execution of the merger agreement, our directors,
executive officers and affiliates entered into support agreements with Columbia
Bancorp and Suburban Bancshares.  The following description of the support
agreement is qualified in its entirety by reference to the support agreement,
copies of which are attached to this proxy statement/prospectus as Appendices B
and C and which are incorporated by reference into this proxy
statement/prospectus.

     Each of the directors, executive officers and affiliates of Columbia
Bancorp and Suburban Bancshares executed the support agreements as a condition
to the completion of the merger.  Under the support agreements, the parties
agreed to vote an aggregate of 21.7% of the outstanding shares of Columbia
Bancorp common stock and an aggregate of 20.0% of the outstanding shares of
Suburban Bancshares common stock in favor of the merger.  The parties also
agreed to vote any additional shares of common stock of Columbia Bancorp or
Suburban Bancshares acquired by the stockholder after the date of the support
agreement.  The support agreements also restrict the power of the stockholders
to transfer their shares of Columbia Bancorp common stock or Suburban Bancshares
common stock, as the case may be, until the completion of the merger or
termination of the merger agreement.  Those Columbia Bancorp and Suburban
Bancshares stockholders who are party to the support agreements have also agreed
that, in their capacity as stockholders, they will not directly or indirectly
solicit, initiate or encourage any inquiries or proposals or participate in any
discussions or negotiations with anyone concerning any merger, acquisition or
similar transaction.

                                      -76-
<PAGE>

                 CERTAIN INFORMATION INCORPORATED BY REFERENCE

     Information relating to principal stockholders and security ownership of
management, executive compensation, various benefit plans (including share
option plans), certain relationships and related transactions and other related
matters as to Columbia Bancorp is set forth in Columbia Bancorp's Annual Report
on Form 10-K for the year ended December 31, 1998 and Quarterly Reports on Form
10-Q for the quarters ended March 31, 1999, June 30, 1999 and September 30,
1999, incorporated herein by reference.  Stockholders of Columbia Bancorp and
Suburban Bancshares desiring a copy of Columbia Bancorp's 1998 Annual Report may
contact Columbia Bancorp by mail at 9171 Baltimore National Pike, Ellicott City,
Maryland  21042 Attention:  John A. Scaldara, Jr. or by telephone at (410) 465-
4800 as indicated under "Where You Can Find More Information on page 98."

     Information relating to principal stockholders and security ownership of
management, executive compensation, various benefit plans (including share
option plans), certain relationships and related transactions and other related
matters as to Suburban Bancshares is set forth in Suburban Bancshares' Annual
Report on Form 10-K for the year ended December 31, 1998, and Quarterly Reports
on Form 10-Q for the quarters ended March 31, 1999, June 30, 1999 and September
30, 1999, incorporated herein by reference.  Stockholders of Suburban Bancshares
and Columbia Bancorp desiring a copy of Suburban Bancshares' 1998 Annual Report
may contact Suburban Bancshares by mail at 7505 Greenway Center Drive, P. O. Box
298, Greenbelt, Maryland  20768-0298, Attention:  Stephen A. Horvath or by
telephone at (301) 474-6694 as indicated under "Where You Can Find More
Information on page __."

                                      -77-
<PAGE>

           COMPARISON OF THE RIGHTS OF HOLDERS OF COLUMBIA BANCORP
              CAPITAL STOCK AND SUBURBAN BANCSHARES CAPITAL STOCK

     Columbia Bancorp and Suburban Bancshares are incorporated in Maryland and
Delaware, respectively. Upon consummation of the merger, stockholders of
Suburban Bancshares, whose rights as stockholders are currently governed by
Delaware General Corporation Law, the Suburban Bancshares charter, and the
Suburban Bancshares bylaws, will automatically become stockholders of Columbia
Bancorp. As stockholders of Columbia Bancorp, their rights will be governed by
the Maryland General Corporation Law and by the Columbia Bancorp charter and the
Columbia Bancorp bylaws. The following is a summary of the material differences
between the rights of holders of Suburban Bancshares capital stock and the
rights of holders of Columbia Bancorp capital stock. The following does not
purport to be a complete description of the differences between the rights of
Columbia Bancorp and Suburban Bancshares stockholders. Such differences may be
determined in full by reference to the Maryland General Corporation Law, the
Delaware General Corporation Law, the Columbia Bancorp charter, the Suburban
Bancshares charter and the Columbia Bancorp bylaws and Suburban Bancshares
bylaws.

     The Maryland General Corporation Law, the Columbia Bancorp charter and
Columbia Bancorp bylaws contain provisions that may be deemed to have an anti-
takeover effect and that may delay, defer or prevent a change in control of
Columbia Bancorp or other transaction that a Columbia Bancorp stockholder might
consider in its best interest, including a transaction that might result in a
premium over the market price for the shares held by Columbia Bancorp
stockholders. These provisions are expected to discourage various types of
coercive takeover practices and inadequate takeover bids and to encourage
persons seeking to acquire control of Columbia Bancorp to negotiate first with
the Columbia Bancorp board. Columbia Bancorp's management believes that the
benefits of these provisions outweigh the potential disadvantages of
discouraging such proposals because, among other things, negotiation of such
proposals might result in an improvement of their terms. Although similar
provisions exist under Delaware law and have been applicable to Suburban
Bancshares, the Suburban Bancshares charter and Suburban Bancshares bylaws do
not contain some of the anti-takeover provisions contained in the Columbia
Bancorp charter.

                           AUTHORIZED CAPITAL STOCK

<TABLE>
<CAPTION>
Columbia Bancorp                                    Suburban Bancshares
- ----------------                                    -------------------
<S>                                                 <C>
10,000,000 shares of common stock, par value        20,000,000 shares of common stock, par value $0.01
$0.01 per share.                                    per share.

Subject to applicable Nasdaq rules and              1,000,000 shares of preferred stock, par value
regulations, the Columbia Bancorp board may         $0.01 per share.
issue, in its discretion, additional shares of
Columbia Bancorp common stock or Columbia           The Suburban Bancshares board may increase or
Bancorp preferred stock; provided, that the         decrease the number of shares of common stock or
total number of shares issued does not exceed       preferred stock, but not below the number of shares
the authorized number of shares of capital stock.   of such class or series then outstanding, subject
                                                    to the rights of the holders of any class or series
                                                    of preferred stock and to applicable Nasdaq rules
                                                    and
</TABLE>

                                      -78-
<PAGE>

<TABLE>
<S>                                                   <C>
</TABLE>
                                                      regulations.

                                 VOTING RIGHTS
<TABLE>
<CAPTION>
Columbia Bancorp                                      Suburban Bancshares
- ----------------                                      -------------------
<S>                                                   <C>
Maryland law provides that, unless otherwise          Delaware law provides that , unless otherwise
provided in a corporation's charter:                  provided in a corporation's charter:

 .  each share of its capital stock is entitled to     .  each share of its capital stock is entitled to one
   one vote;                                             vote;

 .  the presence in person or by proxy of              .  a stockholder with voting rights may authorize
   stockholders entitled to cast a majority of all       another person to act for such stockholder be
   the votes entitled to be cast at a meeting            revocable or irrevocable proxy.
   constitutes a quorum; and
                                                      Delaware law provides that a corporation may
 .  in matters other than the election of directors    designate the voting rights of each class of stock
   or the approval of extraordinary transactions, a   and must specify the voting rights of such class of
   majority of all the votes cast at a meeting at     stock in the certificate of incorporation or the
   which a quorum is present is sufficient to         board resolutions providing for the issuance of
   approve a matter which properly comes before a     stock.
   stockholder meeting.
                                                      Each holder of Suburban Bancshares common stock is
Maryland law limits the voting rights of "control     entitled to one vote per share. Suburban
shares" held by persons who, directly or              Bancshares' certificate of incorporation permits
indirectly, have the power to exercise:               the Suburban Bancshares board to issue Suburban
                                                      Bancshares preferred stock in one or more series
 .  one-fifth or more, but less than one-third;        that may have voting power that differs from that
                                                      of the Suburban Bancshares common stock.
 .  one-third or more, but less than a majority; or

a majority or more of all voting power in the
election of directors. See "State Law Takeover
Legislation."

Subject to Maryland law, each holder of Columbia
Bancorp common stock is entitled to one vote per
share. Columbia Bancorp's charter permits the
Columbia Bancorp board to classify and issue
Columbia Bancorp preferred stock in one or more
series that may have voting power that differs
from that of the Columbia Bancorp common stock.
See "Description of Columbia Bancorp Capital
Stock."
</TABLE>

                                      -79-
<PAGE>

            ADVANCE NOTICE PROVISION/SPECIAL METING OF STOCKHOLDERS

<TABLE>
<CAPTION>
Columbia Bancorp                                    Suburban Bancshares
- ----------------                                    -------------------
<S>                                                 <C>
Maryland law provides that special meetings of      Delaware law provides that special meetings of the
the stockholders of a corporation may be called     stockholders of a corporation may be called by the
by the corporation's board of directors or by       corporation's board of directors or by such other
such other persons as may be authorized in the      persons as may be authorized in the corporation's
corporation's charter or bylaws.                    certificate of incorporation or bylaws.

The Columbia Bancorp bylaws provide that with       At special meetings of stockholders, only the
respect to an annual meeting of stockholders,       business specified in Suburban Bancshares' notice
nominations of persons for election of the          of meeting may be brought before the meeting of
Columbia Bancorp board and the  proposal of         stockholders.
business to be considered by stockholders may be
made only:                                          Under the Suburban Bancshares bylaws, in order for
                                                    a stockholder to nominate a candidate for the
 .  Pursuant to Columbia Bancorp's notice of the     election as a director or propose business for
   meeting,                                         consideration at an annual meeting, the stockholder
                                                    must generally give notice to the Suburban
 .  by the Columbia Bancorp board or                 Bancshares Secretary not less than 90 days from the
                                                    first anniversary of the last annual meeting.
 .  by a stockholder who is entitled to vote at the
   meeting and has complied with the procedures set
   forth in the Columbia Bancorp bylaws.

With respect to special meetings of stockholders,
only the business specified in Columbia
Bancorp's notice of meeting may be brought
before the meeting of stockholders. Nominations
of persons for election to the Columbia Bancorp
board may be made at a special meeting of
stockholders:

 .  pursuant to Columbia Bancorp's notice of the
   meeting,

 .  by the Columbia Bancorp board or

 .  provided that the Columbia Bancorp board has
   determined that directors shall be elected at
   such meeting, by a stockholder who is entitled
   to vote at the meeting and has complied with
   the advance notice provisions set forth in the
   Columbia Bancorp bylaws.
 </TABLE>

                                      -80-
<PAGE>

<TABLE>
<S>                                               <C>
Under the Columbia Bancorp bylaws, in
order for a stockholder to nominate
a candidate for the election as a
director or propose business for
consideration at an annual meeting,
the stockholder must generally give
notice to the Columbia Bancorp Secretary
not more then 90 days or less than 60
days from the first anniversary
of the last annual meeting.
</TABLE>

                        SIZE OF THE BOARD OF DIRECTORS

<TABLE>
<CAPTION>
Columbia Bancorp                                    Suburban Bancshares
- ----------------                                    -------------------
<S>                                                 <C>
Under Maryland law, a corporation must generally    Delaware law provides that the certificate of
have at least three directors at all times.         incorporation or the bylaws of a corporation may
Subject to this provision, a corporation's          allow the stockholders or the board of directors to
bylaws may alter the number of directors and        fix or change the number of directors, but a
authorize a majority of the entire board of         corporation must have at least one director. The
directors to alter within specified limits the      Suburban Bancshares board is currently comprised of
number of directors set by the corporation's        10 members. The Suburban Bancshares bylaws provide
charter or its bylaws. The number of persons        that the number of members of the board of
currently constituting the Columbia Bancorp         directors shall be not less than seven nor more
board is seventeen. The Columbia Bancorp charter    than 20 directors.
provides that the number of persons constituting
the Columbia Bancorp board shall be 25 unless
changed by an amendment to the Columbia Bancorp
bylaws but may never be less than allowed by
law. The Columbia Bancorp bylaws provide that
the number of directors shall be no more than 30
and generally, no less than three.
</TABLE>

                                      -81-
<PAGE>

                   CLASSIFICATION OF THE BOARD OF DIRECTORS

<TABLE>
<CAPTION>
Columbia Bancorcorp                                 Suburban Bancshares
- -------------------                                 -------------------
<S>                                                 <C>
The directors of Columbia Bancorp are divided       Under Delaware law, directors, unless their terms
into three classes, with approximately one-third    are staggered, are elected at each annual
of the directors elected by the stockholders        stockholders meeting. The certificate of
annually. Consequently, members of the Columbia     incorporation may authorize the election of
Bancorp board serve staggered three-year terms.     directors by one or more classes or series of
Classification of the Columbia Bancorp board is     shares, and the certificate of incorporation, an
intended to assure the continuity and stability     initial bylaw or a bylaw adopted by a vote of the
of Columbia Bancorp's business strategies and       stockholders may provide for staggered terms for
policies as determined by the Columbia Bancorp      the directors.
board. The classified board provision of the
Columbia Bancorp bylaws could also have the         The directors of Suburban Bancshares are divided
effect of making the replacement of incumbent       into three classes, with approximately one-third of
directors more time consuming and difficult,        the directors elected by the stockholders annually.
which could delay, defer or prevent an attempt      Consequently, members of the Suburban Bancshares
by a third party to obtain control of Columbia      board serve staggered three-year terms.
Bancorp or cause such transaction to benefit
Columbia Bancorp or its stockholders. At least
two annual meetings of stockholders, instead of
one, will generally be required to effect a
change in a majority of the Columbia Bancorp
board. Thus, the classified board provision
could increase the likelihood that incumbent
directors will retain their positions.
</TABLE>

                      ELECTION OF THE BOARD OF DIRECTORS

<TABLE>
<CAPTION>
Columbia Bancorp                                    Suburban Bancshares
- ----------------                                    -------------------
<S>                                                 <C>
Maryland law provides that a corporation's          Elections for the Suburban Bancshares board are
directors shall be elected by a plurality of the    decided by a plurality of the votes cast.
votes cast at a meeting at which a quorum is
present.                                            Under Delaware law, stockholders do not have
                                                    cumulative voting rights unless the certificate of
Under Maryland law, a corporation's charter may     incorporation so provides. The Suburban Bancshares
provide that stockholders of a corporation can      certificate of incorporation does not grant
elect directors by cumulative voting. Neither       cumulative voting rights to holders of Suburban
the Columbia Bancorp charter nor the Columbia       Bancshares common stock.
Bancorp bylaws grant cumulative voting rights
with respect to the election of directors to
holders of Columbia Bancorp common stock.

Maryland law permits the bylaws of the
corporation to provide for the term of office a
director may serve, except that (1) the term of
</TABLE>

                                      -82-
<PAGE>


<TABLE>
<S>                                                <C>
office of a director may not be longer than five
years or, except in the case of an
initial or substitute director,shorter
than the period annual meetings and (2)
the term of office of at least one class
shall expire each year. The Columbia
Bancorp charter provides for a classified
board.
</TABLE>

                             REMOVAL OF DIRECTORS


<TABLE>
<CAPTION>
Columbia Bancorp                                    Suburban Bancshares
- ----------------                                    -------------------
<S>                                                 <C>
Under Maryland law, unless the corporation's        Under Delaware law, in the case of a corporation
charter provides otherwise, the stockholders of     whose board of directors is classified, except as
a corporation with a classified board of            otherwise provided in a corporation's certificate
directors may remove any director, only for         of incorporation, the stockholders may remove any
cause, by the affirmative vote of a majority of     director only for cause by the vote of a majority
all the votes entitled to be cast for the           of all the votes entitled to be cast in the
election of directors. The Columbia Bancorp         election of the directors. The Suburban Bancshares'
charter provides that directors may be removed      certificate of incorporation provides for the
only by the affirmative vote of the holders of      removal of directors, only for cause, by the
80% of the votes entitled to be cast in the         affirmative vote of the holders of a majority of
election of the directors.                          all classes of outstanding capital stock.
</TABLE>

                               FILLING VACANCIES

<TABLE>
<CAPTION>
Columbia Bancorp                                    Suburban Bancshares
- ----------------                                    -------------------
<S>                                                 <C>
Under the Columbia Bancorp charter and bylaws,      Under Delaware law, unless the certificate of
vacancies in the Columbia Bancorp board caused      incorporation or bylaws provide otherwise, the
by the removal or resignation of a director may     board of directors of a corporation may fill any
be filled by the vote of a majority of the          vacancy on the board, including vacancies resulting
remaining directors or, if the vacancy is caused    from an increase in the number of directors.
by the removal of a director, by the
stockholders at an annual or special meeting,       The Suburban Bancshares bylaws provide that the
and the appointee shall hold  office for the        directors, whether or not a quorum, may by majority
unexpired term of his predecessor, or until his     vote, choose a successor to hold office for the
successor is elected or appointed and is            unexpired portion of the term of a class of the
qualified. Newly created directorships may be       director whose place has been filled. Vacancies
filled by a majority of the entire Columbia         resulting from an increase in the numbers may be
Bancorp board and the appointee shall hold          filled by the directors, whether or not a quorum,
office until the next election of directors by      by majority vote or be filled by the stockholders
the stockholders or may be filled by the            at an annual or special meeting.
stockholders at an annual or special meeting.
</TABLE>


                                      -83-
<PAGE>

                       STANDARD OF CONDUCT FOR DIRECTOR

Columbia Bancorp                         Suburban Bancshares
- ----------------                         -------------------

Under Maryland law, the standard of      Under Delaware law, the standards of
conduct for directors is set forth in    conduct for directors have developed
Section 2-405.1(a) of the Maryland       through written opinions of the
General Corporation Law, which           Delawar courts in cases decided by
requires that a director of a Maryland   them. Generally, directors of Delaware
corporation perform his or her duties    corporations are subject to a duty of
in "good faith," with "a reasonable      loyalty, a duty of care and a duty of
belief" that his or her actions are      candor to the stockholders. The duty
"in the best interests of the            of loyalty requires directors to
corporation" and with the care of an     refrain from self-dealing. According
"ordinarily prudent person in a like     to the Delaware Supreme Court, the
position . . . under similar             duty of care requires "directors . . .
circumstances."                          in managing the corporate affairs . . .
                                         to use that amount of care which
                                         ordinarily careful and prudent men
                                         would use in similar circumstances" and
                                         the duty of candor requires directors
                                         "to disclose fully and fairly all
                                         material information within the board's
                                         control when it seeks stockholder
                                         action." Later case law has established
                                         "gross negligence" as the test for
                                         breach of the standard for the duty of
                                         care in the process of decision-making
                                         by directors.

 LIABILITY OF DIRECTORS; INDEMNIFICATION OF DIRECTORS AND OFFICERS; INSURANCE

Columbia Bancorp                         Suburban Bancshares
- ----------------                         -------------------

Maryland law requires a corporation,     Delaware law provides that a
unless its charter provides otherwise,   corporation may indemnify any person
which Columbia Bancorp's charter does    made a party or threatened to be made
not, to indemnify a director or          a party to any type of proceeding,
officer who has been successful, on      other than an action by or in the
the merits or otherwise, in the          right of the corporation, because he
defense of any proceeding to which the   or she is or was an officer, director,
person made a party by reason of his     employee or agent of the corporation
service in that capacity. Maryland law   or was serving at the request of the
permits a corporation to indemnify its   corporation as a director, officer,
present and former directors and         employee or agent of another
officers, among others, in connection    corporation or entity, against
with any proceeding to which they may    expenses, judgments, fines and amounts
be made a party by reason of their       paid in settlement actually and
service in those or other capacities     reasonably incurred in connection with
unless it is established that:           such proceeding: (1) if he or she
                                         acted in good faith and in a manner he
 .  the act or omission of the director   or she reasonably believed to be in or
   or officer was material to the        not opposed to the best interests of
   matter giving rise to the             the corporation, and (2) in the case
   proceeding and was committed in bad   of a criminal proceeding, he or she
   faith or was the result of active     had no reasonable cause to believe
   and deliberate                        that his or her conduct was unlawful.

                                      -84-
<PAGE>

   dishonesty,
                                         A corporation may indemnify any person
 .  the director or officer actually      made a party or threatened to be made
   received an improper personal         a party to any threatened, pending or
   benefit in money, property or         completed action or suit brought by or
   services, or                          in the right of the corporation
                                         because he or she was an officer,
 .  in the case of any criminal           director, employee or agent of the
   proceeding, the director or officer   corporation, or is or was serving at
   had reasonable cause to believe       the request of the corporation as a
   that the act or omission was          director, officer, employee or agent
   unlawful.                             of another corporation or other
                                         entity, against expenses actually and
The indemnity may include judgments,     reasonably incurred in connection with
penalties, fines, settlements and        such action or suit (1) if he or she
reasonable expenses actually incurred    acted in good faith and (2) in a
by the director or officer in            manner he or she reasonably believed
connection with the proceeding;          to be in or not opposed to the best
provided, however, that if the           interests of the corporation, except
proceeding is one by or in the right     that no indemnification shall be made
of the corporation, indemnification is   if the person is found liable to the
not permitted with respect to any        corporation unless, in such a case,
proceeding in which the director or      the court determines the person is
officer has been adjudged to be liable   entitled to such indemnification.
to the corporation.

In addition, a director or officer may   A corporation must indemnify a
not be indemnified with respect to any   director, officer, employee or agent
proceeding charging improper personal    against expenses actually and
benefit to the director or officer in    reasonably incurred by him or her, who
which the director or officer was        successfully defends himself in a
adjudged to be liable on the basis       proceeding to which he or she was a
that personal benefit was improperly     party by reason of the person's
received. The termination of any         service in that capacity. Expenses
proceeding by conviction or upon a       incurred by an officer or director, or
plea of nolo contendere or its           other employees or agents as deemed
equivalent or an entry of an order of    appropriate by the board of directors,
probation prior to judgment creates a    in defending a civil or criminal
rebuttable presumption that the          proceeding may be paid by the
director or officer did not meet the     corporation in advance of the final
requisite standard of conduct required   disposition of such proceeding upon
for permitted indemnification. The       receipt of an undertaking by or on
termination of any proceeding by         behalf of such director or officer to
judgment, order or settlement,           repay such amount if it shall
however, does not create a presumption   ultimately be determined that he or
that the director or officer did not     she is not entitled to be indemnified
meet the requisite standard of conduct   by the corporation.
for permitted indemnification.
                                         The Delaware law indemnification and
As a condition to advancing expenses     expense advancement provisions are not
to a director who is a party to a        exclusive of any other rights which
proceeding, Maryland law requires        may be granted by the Suburban
Columbia Bancorp to obtain a written     Bancshares bylaws, a vote of
affirmation from the director or         stockholders or disinterested
officer of his good faith belief that    directors or otherwise.
he has met the standard of conduct
necessary for indemnification by         Under Delaware law, termination of any
Columbia Bancorp and a written           suit or other action or its equivalent
statement by or on his behalf to repay   shall not, of itself, create a
the amount paid or reimbursed by         presumption that such person is
Columbia Bancorp if it is ultimately     prohibited from being indemnified.
determined

                                      -85-
<PAGE>

that the standard of conduct was not     The Suburban Bancshares certificate of
met.                                     incorporation provides that each
                                         director, officer and employee of the
The Columbia Bancorp charter provides    corporation shall be indemnified by
that Columbia Bancorp, to the fullest    the corporation to the fullest extent
extent of Maryland law, will             permitted by Delaware law.
indemnify, and advance expenses to a
director or officer of Columbia          Suburban Bancshares
Bancorp.                                 -------------------

          LIMITATION OF PERSONAL LIABILITY OF DIRECTORS AND OFFICERS

Columbia Bancorp                         Suburban Bancshares
- ----------------                         -------------------

Maryland law permits a Maryland          As permitted under Delaware law,
corporation's charter to include a       Suburban Bancshares' certificate of
provision expanding or limiting the      incorporation limits the personal
liability of its directors and           liability of directors, but not
officers to the corporation or its       officers, for monetary damages for
stockholders for money damages, except   breach of such directors' fiduciary
for liability resulting from:            duty.

 .  actual receipt of an improper         The certificate of incorporation
   benefit or profit in money,           further provides for the elimination
   property, or services, in which       or limitation of liability to the
   case recovery is limited to the       fullest extent permitted by Delaware
   actual amount of the benefit or       law.
   profit actually received, or

 .  a judgment or other final
   adjudication adverse to the person
   that is entered in a proceeding
   based on a finding in the
   proceeding that the person's
   action, or failure to act, was
   result of active and deliberate
   dishonesty and was material to the
   cause of action adjudicated in the
   proceeding.

The Columbia Bancorp charter provides
that, to the fullest extent permitted
by law, Columbia Bancorp directors and
officers are not liable to Columbia
Bancorp or its stockholders for money
damages. However, such provisions do
not limit the availability of
equitable relief to Columbia Bancorp
or its stockholders.

                        INSPECTION OF BOOKS AND RECORDS

Columbia Bancorp                         Suburban Bancshares
- ----------------                         -------------------

Maryland law provides that persons who   Delaware law allows any stockholder,
together have been stockholders for      upon written demand under oath stating
more than six months and own at least    the purpose thereof, the right during
5% of the outstanding stock of any       usual hours for business to inspect
class of a Maryland corporation may      for any proper purpose the
inspect and                              corporation's stock ledger,

                                      -86-
<PAGE>

copy the corporation's books of          a list of its stockholders, and its
account and stock ledger, request and    other books and records, and to make
receive a statement of the               copies or extracts therefrom. A proper
corporation's affairs and request and    purpose means a purpose reasonably
receive, within 20 days, a list of its   related to such person's interest as a
stockholders. In addition, any           stockholder.
stockholder of a Maryland corporation
may inspect and copy the bylaws,
minutes of the proceedings of
stockholders and annual statements of
affairs and request the corporation to
provide a sworn statement showing all
stock and securities issued and all
consideration received by the
corporation for such stock during the
preceding twelve months.

                              CHARTER AMENDMENTS

Columbia Bancorp                         Suburban Bancshares
- ----------------                         -------------------

Maryland law allows amendment of a       Delaware law provides that unless a
corporation's charter if its board of    higher vote is required in the
directors adopts a resolution setting    certificate of incorporation, an
forth the amendment proposed,            amendment to the certificate of
declaring its advisability, and the      incorporation of a corporation may be
stockholders thereafter approve such     approved by a majority of the
proposed amendment either at a special   outstanding shares and a majority of
meeting called by the board for the      the outstanding shares of each class
purpose of approval of such amendment    entitled to vote upon the proposed
by the stockholders or, if so directed   amendment.
by the board, at the next annual
stockholders' meeting. At any such       Suburban Bancshares' certificate of
meeting, the proposed amendment must     incorporation provides that the
be approved by two-thirds of all votes   corporation reserves the right to
entitled to vote on the matter. The      amend in any respect any provision of
affirmative vote of holders of at        the certificate of incorporation, in
least 80% of the voting stock of         the manner now or hereafter provided
Columbia Bancorp, however, is required   by law. However, the affirmative vote
to repeal or amend the provisions of     of the holders of not less than 80% of
the Columbia Bancorp charter relating    the outstanding shares entitled to
to the minimum and maximum number, and   vote is required to repeal, rescind,
removal, of directors.                   alter or amend specified provisions
                                         on:

                                         .  the number of directors,

                                         .  personal liability of directors,

                                         .  the provisions requiring that all
                                            actions by stockholders must be
                                            made at duly held annual or special
                                            meetings and may not be taken only
                                            upon written consent,

                                         .  the provisions governing who may
                                            call special meetings and what
                                            matters may be considered at such
                                            special meetings,

                                         .  the provisions concerning the
                                            restrictions on transfer of shares,
                                            and restrictions on acquisitions
                                            and offers by stockholders, and

                                      -87-
<PAGE>

                                         .  the provisions governing amendment
                                            of the certificate of incorporation.

                               BYLAW AMENDMENTS

Columbia Bancorp                         Suburban Bancshares
- ----------------                         -------------------

Under Maryland law, the exclusive        Delaware law provides that a
power to change the bylaws may be left   corporation's bylaws may be amended by
with the stockholders, vested in the     its stockholders, and, if so provided
directors or shared by both groups.      in the corporation's certificate of
The Columbia Bancorp bylaws have         incorporation, by the corporation's
vested the power to adopt, alter and     directors. Suburban Bancshares'
repeal the Columbia Bancorp bylaws in    charter provides that a majority of
the Columbia Bancorp board and the       the Suburban Bancshares board has the
stockholders. Such power may only be     power, at a regular meeting or a
exercised by two-thirds of the entire    special meeting where due notice has
Columbia Bancorp board then in office    been given of the proposed amendment,
or by a vote of the holders of 80% of    to alter, amend or repeal any bylaw of
the stock entitled to vote.              the corporation or create new bylaws.

                                         The provisions governing the number of
                                         directors, election and term of
                                         directors, directors' vacancies, and
                                         amending the bylaws may only be
                                         amended or repealed by the affirmative
                                         vote of the holders of not less than
                                         80% of the outstanding shares of
                                         capital stock of the corporation
                                         entitled to vote generally on the
                                         election of directors thereof.

                                      -88-
<PAGE>

       VOTE ON MERGER, CONSOLIDATION OR SALE OF SUBSTANTIALLY ALL ASSETS

Columbia Bancorp                         Suburban Bancshares
- ----------------                         -------------------

Under Maryland law, unless the           Delaware law provides that, unless
corporate charter states otherwise,      otherwise specified in a corporation's
the approval by the holders of two-      certificate of incorporation, a sale
thirds of the shares of the              or other disposition of all or
corporation entitled to vote on such     substantially all of the corporation's
matters is required for:                 assets, a merger or consolidation of
                                         the corporation with another
 .  sale, lease, exchange or transfer     corporation or a dissolution of the
   of all or substantially all of the    corporation requires the affirmative
   assets of a corporation not in the    vote of the board of directors (except
   ordinary course of business           in limited circumstances) plus, with
   conducted by it, and                  exceptions, the affirmative vote of a
                                         majority of the outstanding stock
 .  any merger, consolidation or share    entitled to vote thereon.
   exchange involving the corporation.

                                         Suburban Bancshares' certificate of
The Columbia Bancorp charter has not     incorporation provides that some
taken any exception to this provision.   business combinations require approval
                                         of the holders of 80% of the
Maryland law also provides that the      outstanding shares of voting stock of
vote of the stockholders of a            Suburban Bancshares and a majority of
surviving corporation is not required    the combined voting power of the
to approve a merger if (1) the plan of   holders of shares of voting stock who
merger does not reclassify or change     are Disinterested Stockholders (that
its outstanding stock or otherwise       is, unrelated to the person or entity
amend the corporation's charter and      with whom Suburban Bancshares is
(2) the number of shares of common       entering the business combination).
stock to be issued or transferred in
the merger does not increase by more
than 20% of the number of its shares
of the same class outstanding
immediately before the merger becomes
effective.

                             STOCKHOLDER MEETINGS

Columbia Bancorp                         Suburban Bancshares
- ----------------                         -------------------

Under Maryland law, a special meeting    Delaware law provides that special
of stockholders may be called by the     meetings of the stockholders of a
president, the board of directors or     corporation may be called by the
any other person specified in the        corporation's board of directors or by
corporation's charter or bylaws. The     such other persons as may be
Columbia Bancorp bylaws provide that     authorized in the corporation's
an annual meeting of stockholders is     certificate of incorporation or
to be held each year on the third        bylaws. The Suburban Bancshares bylaws
Tuesday in April or within 30 days       provide that an annual meeting of
thereof, as designated by the Columbia   stockholders of the corporation is to
Bancorp board. Under the Columbia        be held each year on the first Tuesday
Bancorp bylaws, a special meeting of     in April or at another date as
the stockholders of Columbia Bancorp     designated annually by the Suburban
may be called at any time by             Bancshares board. Under the Suburban
                                         Bancshares bylaws, a special meeting
                                         may only be

                                      -89-
<PAGE>

                                         called by the Suburban Bancshares
                                         board, the chairman of the Suburban
 .  the Chairman of the Board of          Bancshares board, the president or a
   Columbia Bancorp,                     majority of the votes entitled to be
                                         cast at a special meeting.
 .  the President of Columbia Bancorp,
   or

 .  a majority of the Columbia Bancorp
   board.

The Secretary of Columbia Bancorp is
required to call a special meeting of
stockholders upon the written request
of stockholders entitled to cast a
majority of all the votes entitled to
be cast at a special meeting. Such a
request must state the purpose of the
meeting and matters proposed to be
acted on. The stockholders calling
such a special meeting are required to
reimburse Columbia Bancorp for the
costs of preparing and mailing a
notice of such a meeting to the
stockholders.

                      CORPORATE ACTION WITHOUT A MEETING

Columbia Bancorp                         Suburban Bancshares
- ----------------                         -------------------

Under Maryland law, any action           Delaware law provides that any action
required or permitted to be taken at a   required or permitted at a
meeting of stockholders may be taken     stockholders' meeting may be taken
without a meeting if (1) a unanimous     without a meeting if a majority of the
written consent setting forth the        holders of the outstanding shares
action and signed by each stockholder    consent in writing.
entitled to vote on such matters and
(2) a written waiver of any right to     Under Suburban Bancshares' certificate
dissent signed by each stockholder       of incorporation, action may be taken
entitled to notice of the meeting but    by the unanimous written consent of
not entitled to vote at it, are filed    the stockholders entitled to vote on
with the records of the stockholders     the matter.
meeting. The Columbia Bancorp bylaws
permit corporate action without a
meeting of stockholders in accordance
with the parameters set forth in
Maryland law. Because Maryland law
requires the unanimous written consent
of all stockholders entitled to vote
for actions by written consent, it is
unlikely that stockholders of Columbia
Bancorp will be able to take action by
written consent under Maryland law.
This provision of Maryland law may
deter hostile takeovers, as a holder
or group of holders controlling a
majority in interest of Columbia
Bancorp common stock will not be able
to amend the Columbia Bancorp bylaws
or remove directors pursuant to a
stockholders' written consent unless
they obtain a unanimous written

                                      -90-
<PAGE>

consent of all stockholders or call a
special meeting of the stockholders.

                                   DIVIDENDS

Columbia Bancorp                         Suburban Bancshares
- ----------------                         -------------------

Under Maryland law, the board of         Subject to any restrictions contained
directors has the power to authorize     in a corporation's certificate of
and cause the corporation to pay         incorporation, Delaware law generally
distributions in cash, property or       provides that a corporation may
securities of the corporation unless     declare and pay dividends out of
the declaration of such distributions    "surplus," which means the excess, if
would be contrary to the charter.        any, of net assets over capital or
                                         when no surplus exists, out of new
Maryland law further provides that no    profits for the fiscal year in which
distribution may be made (1) if the      the dividend is declared and/or the
corporation would become unable to pay   preceding fiscal year. Dividends may
its debts as they become due in the      not be paid, however, out of net
usual course of business or (2) the      profits if the capital of the
corporation's total assets would be      corporation is less than the amount of
less than the sum of its liabilities     capital represented by the issued and
plus, unless the charter permits         outstanding stock of all classes
otherwise, the amount that would be      having a preference upon the
needed, if the corporation were to be    distribution of assets. In accordance
dissolved at the time of the             with Delaware law, "capital" is
distribution, to satisfy the             determined by the board of directors
preferential rights upon dissolution     and shall not be less than the
of stockholders whose preferential       aggregate par value of the outstanding
rights on dissolution are superior to    capital stock of the corporation
those receiving the distribution.        having par value.

                                         Suburban Bancshares' bylaws provide
                                         that dividends may be declared at any
                                         regular or special meeting, pursuant
                                         to law. Dividends may be paid in cash,
                                         in property or in the corporation's
                                         own shares, subject to the provisions
                                         of any statute and of the certificate
                                         of incorporation, which does not speak
                                         to dividends.

                        APPRAISAL OR DISSENTERS' RIGHTS


Columbia Bancorp                         Suburban Bancshares
- ----------------                         -------------------

Under Maryland law, stockholders of a    Under Delaware law, a stockholder of a
corporation are entitled to              Delaware corporation may be entitled
dissenters' rights of appraisal in       to demand appraisal and obtain payment
connection with a:                       of the judicially determined fair
                                         value of his or her shares in the
 .  Merger or consolidation,              event of any plan of merger or
                                         consolidation in which the
 .  Share exchange,                       corporation, the shares of which he or
                                         she holds, is a party, provided such
 .  Transfer of assets requiring          stockholder continuously holds such
   stockholder approval                  shares through the effective date of
                                         the merger, otherwise complies with
 .  Amendment of charter which alters     the requirements of Delaware law for
   the contract                          the perfection of appraisal

                                      -91-
<PAGE>

   rights of any outstanding stock and   rights and does not vote in favor of
   substantially adversely affects       the merger. However, this right to
   stockholder rights if the right to    demand appraisal does not apply to
   do so is not reserved in the          stockholders if:
   charter, or
 .  Business combination transaction.     (i)   they are stockholders of a
                                         surviving corporation and if a vote of
However, except with respect to          the stockholders of such corporation
transactions involving an interested     is not necessary to authorize the
stockholder, stockholders generally      merger or consolidation; or
have no dissenter's right of appraisal
with respect to their shares if:         (ii)  the shares held by the
                                         stockholders are the shares are listed
 .  The shares are listed on a national   on a national securities of a class or
   securities exchange or are            series listed on a national exchange
   designated as a national market       or are designated as a national
   system security on an interdealer     securities exchange, designated as a
   quotation system by the National      national market system security on an
   Association of Securities Dealers,    interdealer market system by the
   Inc. or                               National Association quotation system
                                         by the NASD, or

 .  The shares are that of the            (iii) are held of record by more than
   successor in the merger, unless (1)   2,000 stockholders on the date set to
   the merger alters the contractual     determine the stockholders entitled to
   rights of the shares as expressly     vote on the merger or consolidation.
   set forth in the charter and the
   charter does not reserve the right    Notwithstanding the above, appraisal
   to do so or (2) the shares are to     rights are available for the shares of
   be changed or converted in whole or   any class or series of stock of a
   in part in the merger into            Delaware corporation if the holders
   something other than either shares    thereof are required by the terms of
   in the successor or cash, scrip, or   the agreement of merger or
   other rights or interests arising     consolidation to accept for their
   out of the provisions for the         stock anything except: (i) shares of
   treatment of fractional shares in     stock of the corporation surviving or
   the successor.                        resulting from the merger or
                                         consolidation; (ii) shares of stock of
Accordingly, Columbia Bancorp            any other corporation which at the
stockholders are not generally           effective date of the merger or
entitled to appraisal rights.            consolidation will be listed on The
                                         New York Stock Exchange or the
                                         American Stock Exchange, designated as
                                         a national market system security on
                                         an interdealer quotation system by the
                                         NASD or are held of record by more
                                         than 2,000 stockholders; or (iii) cash
                                         in lieu of fractional shares of the
                                         corporations described in (i) or (ii);
                                         or (iv) any combination of shares of
                                         stock and cash in lieu of fractional
                                         shares described in (i), (ii) and
                                         (iii).

                                         A Delaware corporation may provide in
                                         its certificate of incorporation that
                                         appraisal rights shall be available
                                         for the shares of any class or series
                                         of its stock as the result of an
                                         amendment to its certificate of
                                         incorporation, any merger or

                                      -92-
<PAGE>

<TABLE>
<S>                                                 <C>
                                                    consolidation to which the corporation is a party
                                                    or a sale of all or substantially all of the assets
                                                    of the corporation. The Suburban Bancshares
                                                    certificate of incorporation does not contain any
                                                    provision regarding appraisal rights.

                                                    Consequently, because Suburban Bancshares' common
                                                    stock is quoted on the Nasdaq SmallCap Stock
                                                    Market, appraisal rights are available to holders
                                                    of Suburban Bancshares stock.  If the merger is
                                                    completed, Suburban Bancshares stockholders who do
                                                    not vote for the adoption of the merger agreement
                                                    and who otherwise comply with Section 262 of
                                                    Delaware law will be entitled to appraisal rights
                                                    under Delaware law.

                               DERIVATIVE SUITS

Columbia Bancorp                                    Suburban Bancshares
- ----------------                                    -------------------

There is no statutory right to bring derivative     Under Delaware law, Suburban Bancshares
suit under Maryland law; however, there is a        stockholders have the right to bring a derivative
clear common law right in Maryland to bring a       suit.
derivative suit.

                        STATE LAW TAKEOVER LEGISLATION

Columbia Bancorp                                    Suburban Bancshares
- ----------------                                    -------------------

Under Maryland law, many business combinations,     In general, Delaware law prevents an "Interested
including a merger, consolidation, share            Stockholder" (defined generally as a person with
exchange or a significant asset transfer or         15% or more of a corporation's outstanding voting
issuance or reclassification of equity              stock), from engaging in a "Business Combination"
securities, between a Maryland corporation and      with a Delaware corporation for three years
an interested stockholder who beneficially owns     following the date such person became an Interested
10% or more of the voting power of the              Stockholder. The term "Business Combination"
corporation's shares or an affiliate or             includes among other things, a merger,
associate (as defined in Maryland law) of the       consolidation, sale of assets or share exchange.
corporation who, at any time within the two-year    The three-year moratorium may be avoided if:
period prior to the date in question, was the
beneficial owner of 10% or more of the voting       .  before such person became an Interested
power of the then-outstanding voting stock of          Stockholder, the board of directors of the
the corporation or an affiliate thereof are            corporation approved either the Business
prohibited for five years after the most recent        Combination or the transaction in which the
date on which the interested stockholder becomes       Interested Stockholder became an Interested
an interested stockholder. Thereafter, any such        Stockholder;
business combination must be recommended by the
board of directors of the corporation and
approved by the
</TABLE>

                                      -93-
<PAGE>

<TABLE>
<S>                                                 <C>
affirmative vote of at least (1) 80% of the votes   .  upon consummation of the transaction which resulted
entitled to be cast by holders of outstanding          in the stockholder becoming an Interested
voting shares of the corporation and (2) two-          Stockholder, the stockholder owned at least 85% of
thirds of the votes entitled to be cast by holders     the voting stock of the corporation outstanding at
of outstanding voting shares of the corporation        the time the transaction commenced, excluding
other than shares held by the interested               shares held by directors who are also officers of
stockholder with whom (or with whose affiliate)        the corporation and by employee stock ownership
the business combination is to be effected or by       plans that do not provide employees with the right
an affiliate or associate of the interested            to determine confidentially whether shares held
stockholder, unless, among other conditions, the       subject to the plan will be tendered in a tender or
corporation's common stockholders receive a            exchange offer; or
minimum price (as defined in Maryland law) for
their shares and the consideration is received in   .  on or following the date on which such person
cash or in the same form as previously paid by the     became an Interested Stockholder, the Business
interested stockholder for its shares.                 Combination is approved by the board of directors
                                                       of the corporation and authorized at an annual or
These provisions of Maryland law do not apply,         special meeting of stockholders  (not by written
however, to business combinations that are             consent) by the affirmative vote of the
approved or exempted by the board of directors         stockholders of at least 66 2/3% of the outstanding
of the corporation prior to the time that the          voting stock of the corporation not owned by the
interested stockholder becomes an interested           Interested Stockholder.
stockholder.
                                                    The Business Combination restrictions described
Maryland law also provides that "control shares"    above do not apply if, among other things:
of a Maryland corporation acquired in a "control
share acquisition" have no voting rights except     .  the corporation's original certificate of
to the  extent approved by a vote of two-thirds        incorporation contains a provision expressly
of the votes entitled to be cast on the matter,        electing not to be governed by the statute;
excluding shares owned by the acquiror, by
officers or by directors who are employees of       .  the corporation by action of the holders of a
the corporation. "Control shares" are voting           majority of the voting stock of the corporation
shares which, if aggregated with all other such        approves an amendment to its certificate of
shares previously acquired by the acquiror, or         incorporation or bylaws expressly electing not to
in respect of which the acquiror is able to            be governed by the statute, which amendment shall
exercise or direct the exercise of voting power        not be applicable to any business combination with
(except solely by virtue of a revocable proxy),        a person who was an Interested Stockholder at or
would entitle the acquiror to exercise voting          prior to the time of the amendment; or
power in electing directors within one of the
following ranges of voting power:                   .  the corporation does not have a class of voting
                                                       stock that is (a) listed on a national securities
 .  One-fifth or more but less than one-third,          exchange, (b) authorized for quotation on Nasdaq or
                                                       a similar quotation system; or (c) held of record
 .  One-third or more but less than a majority, or      by more than 2,000 stockholders

 .  A majority or more of all voting power.

Control shares do not include shares the
acquiring person is then entitled to vote as a
result of having previously obtained stockholder
approval. A "control share acquisition" means
the acquisition of
</TABLE>

                                      -94-
<PAGE>

<TABLE>
<S>                                                     <C>
control shares, subject to exceptions. A person            (unless an Interested Stockholder transaction prompted
who has made or proposes to make a control share           any of the foregoing results).
acquisition, upon satisfaction of various
conditions (including an undertaking to pay             The statute also does not apply to Business
expenses), may compel the board of directors of         Combinations with an Interested Stockholder when
the corporation to call a special meeting of            such combination is proposed after the public
stockholders to be held within 50 days of demand        announcement of, and before the consummation or
to consider the voting rights of the shares. If no      abandonment of, a merger or consolidation, a sale
request for a meeting is made, the corporation may      of 50% or more of the aggregate market value of the
itself present the question at any stockholders         assets of the corporation on a consolidated basis
meeting. If voting rights are not approved at the       or the aggregate market value of all outstanding
meeting or if the acquiring person does not             shares of the corporation, or a tender offer for
deliver an acquiring person statement as required       50% or more of the outstanding voting shares of the
by the statute, then the corporation may generally      corporation, if the triggering transaction is with
redeem any or all of the control shares (except         or by a person who either was not an Interested
those for which voting rights have previously been      Stockholder during the previous three years or who
approved) for fair value determined, without            became an Interested Stockholder with the approval
regard to the absence of voting rights for the          of the board, and if the transaction is approved or
control shares, as of the date of the last control      not opposed by a majority of the current directors
share acquisition by the acquiror or of any             who were also directors prior to any person
meeting of stockholders at which the voting rights      becoming an Interested Stockholder during the
of such shares are considered and not approved. If      previous three years.
voting rights for control - shares are approved at
a stockholders meeting and the acquiror becomes         Although Suburban Bancshares could opt out of the
entitled to vote a majority of the shares entitled      provisions of this statute, it has not done so. In
to vote, all other stockholders may exercise            addition, Suburban Bancshares' certificate of
appraisal rights. The fair value of the shares as       incorporation provides that the affirmative vote of:
determined for purposes of such appraisal rights
may not be less than the highest price per share        .  the holders of not less than 80% of the outstanding
paid by the acquiror in the control share                  shares of capital stock entitled to vote generally
acquisition, and limitations and restrictions              in the election of directors; and
otherwise applicable to the exercise of appraisal
rights do not apply in the context of a control         .  the holders of a majority of shares of capital
share acquisition.                                         stock with such voting rights who are disinterested
                                                           stockholders, that is, a stockholder who is not a
The control share acquisition statute does not             related person or an affiliate of a related person,
apply to shares acquired in a merger,                      shall be required for the approval or authorization
consolidation or share exchange, if the                    of any business combination with a related person.
corporation is a party to the transaction, or to
acquisitions approved or exempted by a provision           A related person is any individual, corporation,
in the charter or bylaws of the corporation                partnership or other person or entity which
adopted before the acquisition of shares.                  beneficially owns 10% or more of the capital stock
                                                           with voting rights of the corporation.

                                                           Delaware does not have a control share acquisition
                                                           statute.
</TABLE>

                                      -95-
<PAGE>

                 DESCRIPTION OF COLUMBIA BANCORP CAPITAL STOCK

General

     Columbia Bancorp's authorized capital sock consists of 10,000,000 shares of
common stock, par value $.01 per share. The board of directors may classify and
reclassify any unissued shares of capital stock by setting or changing in any
one or more respects the preferences, conversion or other rights, voting powers,
restrictions, limitations as to dividends, qualifications, or terms or
conditions of redemption of such shares of stock.  The following description
does not contain all the information that might be important to you; therefore,
you should read carefully the more detailed provisions of the Columbia Bancorp
charter and by-laws.  The following summary does not give effect to provisions
of statutory or common law, the provisions of applicable laws and the Columbia
Bancorp charter, which is incorporated by reference as exhibits to the
registration of Form S-4 of which this proxy statement/prospectus is a part.

Common Stock

     As of _____, 1999, there were ___ shares of Columbia Bancorp common stock
outstanding.  A holder of common stock has one vote for each share held by him
on all matters submitted to a vote of stockholders and the exclusive voting
power for all purposes is vested in the holders of the common stock.  Holders of
common stock do not have the right of cumulative voting in connection with the
election of directors.  The common stock has no conversion rights and is not
subject to redemption.  A stockholder of Columbia Bancorp has no preemptive
rights to subscribe for additional shares of stock or other securities of
Columbia Bancorp except as may be granted by the board of directors.

     The holders of common stock of Columbia Bancorp are entitled to receive,
pro rata, dividends when, as and if declared by the board of directors from
funds legally available therefor.  The ability of Columbia Bancorp to pay
dividends to its stockholders is limited primarily by the ability of Columbia
Bank to pay dividends to Columbia Bancorp.  In the event of any liquidation,
dissolution or winding up of Columbia Bancorp the holders of common stock are
entitled to share ratably in all the remaining assets.

     All of the outstanding shares of common stock are, and the shares of common
stock offered hereby will be, validly issued, fully paid and nonassessable.

     The Transfer Agent for the common stock is Registrar and Transfer Company.

Preferred Stock

     Under the Columbia Bancorp charter, the Columbia Bancorp is authorized
without further stockholder action, from time to time, to classify any unissued
shares of capital stock as preferred stock and to issue shares of preferred
stock of Columbia Bancorp, in one or more series, with such designations,
preferences, powers and relative participating, optional or other special
rights, and the qualifications, limitations or restrictions thereon, including,
but not limited to, dividend rights, dividend rate or rates, conversion rights,
voting rights, rights and terms of redemption, the redemption price or

                                      -96-
<PAGE>

prices, and the liquidation preferences as shall be stated in the resolution
providing for the issued of a series of such stock adopted, at any time or from
time to time, by the Columbia Bancorp board.

                                      -97-
<PAGE>

                         FUTURE STOCKHOLDER PROPOSALS

     Pursuant to Rule 14a-8 promulgated under the Exchange Act, Columbia Bancorp
stockholders may present proposals for inclusion in the Columbia Bancorp proxy
statement for consideration at the next annual meeting of its stockholders by
submitting their proposals to Columbia Bancorp in a timely manner. Suburban
Bancshares stockholders who become stockholders of Columbia Bancorp may present
proposals for inclusion in the Columbia Bancorp proxy statement for its 2000
annual meeting, as the date for inclusion in the proxy statement for the 1999
annual meeting has already passed. Any such proposal must comply with Rule
14a-8.

     Columbia Bancorp's by-laws require stockholders who intend to propose
business for consideration by stockholders at an annual meeting, other than
stockholder proposals that are included in the proxy statement, to give written
notice to the Secretary of Columbia Bancorp not less than sixty days and not
more than ninety days before the anniversary of the prior years' meeting.  A
stockholder must submit a matter to be raised at Columbia Bancorp's 2000 meeting
of Stockholders on or after January 28, 2000, but not later than, February 25,
2000.  The written notice should be sent to Columbia Bancorp's principal office
(to the attention of the Secretary) and must include a brief description of the
business, the reasons for conducting such business, any material interest the
stockholder has in such business, the name and address of the stockholder as
they appear on Columbia Bancorp's books and the number of shares of Columbia
Bancorp common stock the stockholder beneficially owns.

     SEC rules set forth standards for what stockholder proposals Columbia
Bancorp is required to include in a proxy statement for an annual meeting.

                                 OTHER MATTERS

     The boards of directors of Columbia Bancorp and Suburban Bancshares do not
know of any other business to be presented for consideration at the meetings.
If other matters properly come before the meetings, the persons named in the
accompanying forms of proxy intend to vote on such matters based on their best
judgment.


     Columbia Bancorp will bear the cost of the meeting and the cost of
soliciting proxies, including the cost of mailing the proxy materials.  In
addition to solicitation by mail, directors, officers and regular employees of
Columbia Bancorp (none of whom will be specifically compensated for such
services) may solicit proxies by telephone or otherwise.  Arrangements will be
made with brokerage houses and other custodians, nominees and fiduciaries to
send proxy cards and proxy materials to the stockholders they represent and
Columbia Bancorp will reimburse them for their expenses.

     Columbia Bancorp will furnish, without charge, to each person whose proxy
is being solicited, upon request, a copy of its Annual Report on Form 10-K for
the fiscal year ended December 31, 1998, as filed with the SEC, including the
financial statements, notes to the financial statements and the financial
schedules contained in the report.  Columbia Bancorp will also furnish copies of
any exhibits to the report but may charge a reasonable copying charge.
Stockholders should address requests for copies of any of these materials to
John A. Scaldara, Jr., Columbia Bancorp, Inc., 9171 Baltimore National Pike,
Ellicott City, Maryland  21042.

                                      -98-
<PAGE>

     Suburban Bancshares will bear the cost of the meeting and the cost of
soliciting proxies, including the cost of mailing the proxy materials.  In
addition to solicitation by mail, directors, officers and regular employees of
Suburban Bancshares (none of whom will be specifically compensated for such
services) may solicit proxies by telephone or otherwise.  Arrangements will be
made with brokerage houses and other custodians, nominees and fiduciaries to
send proxy cards and proxy materials to the stockholders they represent and
Suburban Bancshares will reimburse them for their expenses.

     Suburban Bancshares will furnish, without charge, to each person whose
proxy is being solicited, upon request, a copy of its Annual Report on Form 10-K
for the fiscal year ended December 31, 1998, as filed with the SEC, including
the financial statements, notes to the financial statements and the financial
schedules contained in the report.  Suburban Bancshares will also furnish copies
of any exhibits to the report but may charge a reasonable copying charge.
Stockholders should address requests for copies of any of these materials to
Stephen A. Horvath, Suburban Bancshares, Inc., 7505 Greenway Center Drive, P. O.
Box 298, Greenbelt, Maryland 20768-0298.

     We may engage on or more proxy solicitation firms to assist in obtaining
proxies from our stockholders on a timely basis.  As of the date of this proxy
statement/prospectus, neither of us has engaged a proxy solicitation firm or has
committed ourselves to the payment of any fees for this service.

                                 LEGAL MATTERS

     Piper Marbury Rudnick & Wolfe LLP has issued a legal opinion concerning the
legality of the common stock of Columbia Bancorp to be issued to Suburban
Bancshares stockholders. Certain federal income tax consequences and other
matters relating to the merger will be passed upon by Piper Marbury Rudnick &
Wolfe LLP.  Certain matters relating to the merger will be passed upon by
McNamee, Hosea, Jernigan & Kim, P.A., as counsel to Suburban Bancshares.

                                    EXPERTS

     The financial statements of Columbia Bancorp as of December 31, 1998 and
1997, and for each of the years in the three-year period ended December 31,
1998, have been incorporated by reference herein and in the registration
statement in reliance upon the report of KPMG LLP, independent certified public
accountants, incorporated by reference herein, and upon the authority of said
firm as experts in accounting and auditing.

     The consolidated financial statements of Suburban Bancshares, Inc. at
December 31, 1998 and 1997, and for each of the three years in the period ended
December 31, 1998, have been incorporated by reference herein and in the
registration statement in reliance upon the report of Stegman & Company,
independent certified public accountants, incorporated by reference herein, and
upon the authority of that firm as experts in accounting and auditing.

                                      -99-
<PAGE>

                      WHERE YOU CAN FIND MORE INFORMATION

     Columbia Bancorp has filed with the SEC a registration statement under the
Securities Act that registers the distribution to Suburban Bancshares
stockholders of the shares of Columbia Bancorp common stock to be issued in
connection with the merger. The registration statement, including the attached
exhibits and schedules, contains additional relevant information about Columbia
Bancorp and Columbia Bancorp common stock. The rules and regulations of the SEC
allow us to omit certain information included in the registration statement from
this proxy statement/prospectus.

     In addition, Columbia Bancorp and Suburban Bancshares file annual,
quarterly and special reports, proxy statements and other information with the
SEC under the Securities Exchange Act. You may read and copy this information at
the SEC's Public Reference Room, 450 Fifth Street, N.W., Room 1024, Washington,
D.C. 20549.

     You may also obtain copies of this information by mail from the Public
Reference Section of the SEC, 450 Fifth Street, N.W., Room 1024, Washington,
D.C. 20549, at prescribed rates.  You may obtain information on the operation of
the Public Reference Room by calling the SEC at 1-800-SEC-0330.  The SEC also
maintains an Internet world wide web site that contains reports, proxy
statements and other information about issuers, like Columbia Bancorp and
Suburban Bancshares, who file electronically with the SEC. The address of the
site is http://www.sec.gov.

     The SEC allows us to "incorporate by reference" information into this proxy
statement/prospectus.  This means that we can disclose important information to
you by referring you to another document filed separately with the SEC. The
information incorporated by reference is considered to be a part of this proxy
statement/prospectus, except for any information that is superseded by
information that is included directly in this proxy statement/prospectus.


                                     -100-
<PAGE>

     This proxy statement/prospectus incorporates by reference the documents
listed below that Columbia Bancorp and Suburban Bancshares previously filed with
the SEC. They contain important information about the companies and their
financial condition.

     Columbia Bancorp Commission Filings      Period or Date Filed
     -----------------------------------      --------------------

     Annual Report on Form 10-K               Year ended December 31, 1998
     Quarterly Report on Form 10-Q            Quarter ended March 31, 1999
     Quarterly Report on Form 10-Q            Quarter ended June 30, 1999
     Quarterly Report on Form 10-Q            Quarter ended September 30, 1999
     Current Report on Form 8-K               October 4, 1999

     Suburban Bancshares Commission Filings   Period or Date Filed
     --------------------------------------   --------------------

     Annual Report on Form 10-K               Year ended December 31, 1998
     Quarterly Report on Form 10-Q            Quarter ended March 31, 1999
     Quarterly Report on Form 10-Q            Quarter ended June 30, 1999
     Quarterly Report on Form 10-Q            Quarter ended September 30, 1999
     Current Report on Form 8-K               October 1, 1999

     This proxy statement/prospectus is accompanied by copies of Columbia
Bancorp's Annual Report on Form 10-K for the year ended December 31, 1998, Proxy
Statement dated March 24, 1999 for its Annual Meetings of Stockholders held on
April 27, 1999 and Quarterly Report on Form 10-Q for the quarter ended September
30, 1999.

     This proxy statement/prospectus is also accompanied by copies of Suburban
Bancshares' Annual Report on Form 10-K for the year ended December 31, 1998,
Proxy Statement dated April 22, 1999 for its Annual Meetings of Stockholders
held on May 19, 1999 and Quarterly Report on Form 10-Q for the quarter ended
September 30, 1999.

     We also incorporate by reference additional documents that either company
may file with the SEC between the date of this proxy statement/prospectus and
the date of the Columbia Bancorp or Suburban Bancshares special meetings. These
documents include periodic reports, such as annual reports on Form 10-K,
quarterly reports on Form 10-Q and current reports on Form 8-K, as well as proxy
statements.

     Columbia Bancorp has supplied all information contained or incorporated by
reference in this proxy statement/prospectus relating to Columbia Bancorp, as
well as all pro forma financial information, and Suburban Bancshares has
supplied all information relating to Suburban Bancshares.

     Documents incorporated by reference are available from Columbia Bancorp and
Suburban Bancshares without charge, excluding any exhibits to those documents
unless the exhibit is specifically incorporated by reference as an exhibit in
this proxy statement/prospectus. You can obtain documents incorporated by
reference in this proxy statement/prospectus by requesting them in writing or by
telephone from the appropriate company at the following addresses:

                                     -101-
<PAGE>

     Columbia Bancorp                  Suburban Bancshares, Inc.
     9171 Baltimore National Pike      7505 Greenway Center Drive, P. O. Box 298
     Ellicott City, Maryland 21042     Greenbelt, Maryland 20768-0298
     Phone: (410) 465-4800             Phone: (301) 474-6694

     If you would like to request documents, please do so by ___________, 1999
to receive them before the special meeting. If you request any incorporated
documents from Columbia Bancorp or Suburban Bancshares, we will mail them to you
by first class mail, or another equally prompt means, within one business day
after we receive your request.

     We have not authorized anyone to give any information or make any
representation about the merger or our companies that is different from, or in
addition to, that contained in this proxy statement/prospectus or in any of the
materials that have been incorporated into this proxy statement/prospectus.
Therefore, if anyone does give you information of this sort, you should not rely
on it. If you are in a jurisdiction where offers to exchange or sell, or
solicitations of offers to exchange or purchase, the securities offered by this
proxy statement/prospectus or the solicitation of proxies is unlawful, or if you
are a person to whom it is unlawful to direct these types of activities, then
the offer presented in this proxy statement/prospectus does not extend to you.
The information contained in this proxy statement/prospectus speaks only as of
the date of this proxy statement/prospectus unless the information specifically
indicates that another date applies.

                                     -102-
<PAGE>

                                  APPENDIX A


                         AGREEMENT AND PLAN OF MERGER

                                      A-1
<PAGE>

                          PLAN AND AGREEMENT TO MERGE

                               TABLE OF CONTENTS

<TABLE>
<CAPTION>
         <S>                                                                                                      <C>
         1.    Effective Date...............................................................................      7
         2.    Events Preceding Effectiveness...............................................................      7
         3.    Representations and Warranties of Suburban Bancshares........................................      9
         3.1.  Organization, Standing, and Capitalization of Suburban Bancshares and the
               Suburban Subsidiaries........................................................................      9
         3.2.  Financial Statements.........................................................................     10
         3.3.  Taxes........................................................................................     10
         3.4.  No Undisclosed Liabilities...................................................................     11
         3.5.  Absence of Certain Changes or Events.........................................................     11
         3.6.  Complete and Accurate Disclosure.............................................................     11
         3.7.  Title to Properties; Absence of Liens and Encumbrances; Compliance with Laws.................     12
         3.8.  Contracts....................................................................................     12
         3.9.  Litigation, Etc..............................................................................     14
         3.10  Environmental Matters........................................................................     14
         3.11. Labor Matters................................................................................     16
         3.12. Pension and Welfare Matters..................................................................     16
         3.13. Related Party Transactions...................................................................     20
         3.14. No Conflict with Other Documents.............................................................     20
         3.15. Compliance with Laws; Governmental Authorizations............................................     20
         3.16. Authority; Enforceability....................................................................     21
         3.17. Insurance....................................................................................     21
         3.18. Financial Institutions Bond..................................................................     21
         3.19. Brokers; Financial Advisor...................................................................     21
         3.20. Beneficial Ownership of Columbia Bancorp Common Stock........................................     22
         3.21. Year 2000....................................................................................     22
         4.    Representations and Warranties of Columbia Bancorp...........................................     22
         4.1.  Organization, Standing, and Capitalization of Columbia Bancorp and Columbia
               Subsidiaries.................................................................................     22
         4.2.  Financial Statements.........................................................................     24
         4.3.  Taxes........................................................................................     24
         4.4.  No Undisclosed Liabilities...................................................................     24
         4.5.  Absence of Certain Changes or Events.........................................................     25
</TABLE>

                                      A-2
<PAGE>

<TABLE>
<CAPTION>
         <S>                                                                                                     <C>
         4.6.  Complete and Accurate Disclosure.............................................................     25
         4.7.  Title to Properties; Absence of Liens and Encumbrances; Compliance with Laws.................     25
         4.8.  Contracts....................................................................................     26
         4.9.  Litigation, Etc..............................................................................     27
         4.10. Environmental Matters........................................................................     28
         4.11. Labor Matters................................................................................     29
         4.12. Pension and Welfare Matters..................................................................     29
         4.13. Related Party Transactions...................................................................     33
         4.14. No Conflict with Other Documents.............................................................     33
         4.15. Compliance with Laws; Governmental Authorizations............................................     33
         4.16. Authority; Enforceability....................................................................     34
         4.17. Insurance....................................................................................     34
         4.18. Financial Institutions Bond..................................................................     34
         4.19. Brokers; Financial Advisor...................................................................     34
         4.20. Beneficial Ownership of Suburban Bancshares Common Stock.....................................     35
         4.21. Year 2000....................................................................................     35
         5.    Covenants of Suburban Bancshares.............................................................     35
         5.1.  Information..................................................................................     35
         5.2.  Events Preceding Effectiveness...............................................................     36
         5.3.  Regulatory Approvals.........................................................................     36
         5.4.  Conduct of Business..........................................................................     36
         5.5.  Reservation of Shares........................................................................     37
         5.6.  Meeting of Stockholders of Suburban Bancshares; Document Preparation.........................     37
         5.7.  Consents.....................................................................................     38
         5.8.  Current Information; Advice of Changes.......................................................     38
         5.9.  No Solicitation of Other Offers..............................................................     39
         5.10  Affiliate Agreements.........................................................................     40
         5.11. Pooling-of-Interests.........................................................................     40
         5.12. Taxes........................................................................................     40
         5.13. Public Announcements.........................................................................     41
         6.    Covenants of Columbia Bancorp................................................................     41
         6.1.  Information..................................................................................     41
         6.2.  Events Preceding Effectiveness...............................................................     42
         6.3.  Applications to Governmental Regulatory Authorities..........................................     42
         6.4.  Conduct of Business..........................................................................     42
</TABLE>
                                      A-3
<PAGE>

<TABLE>
<CAPTION>
         <S>                                                                                                     <C>
         6.5   Columbia Bancorp Common Stock.................................................................    43
         6.6.  Registration of Shares........................................................................    43
         6.7.  Meeting of Stockholders of Columbia Bancorp; Document Preparation.............................    44
         6.8.  Consents......................................................................................    45
         6.9.  Current Information; Advice of Changes........................................................    45
         6.10  No Solicitation of Other Offers...............................................................    45
         6.11. Affiliate Agreements..........................................................................    46
         6.12. Pooling-of-Interests..........................................................................    46
         6.13. Taxes.........................................................................................    46
         6.14. Public Announcements..........................................................................    47
         7.    Conditions Precedent to Columbia Bancorp's Obligations........................................    47
         7.1.  Representations, Warranties, and Covenants....................................................    47
         7.2.  No Adverse Changes............................................................................    47
         7.3.  Events Preceding the Effective Date...........................................................    47
         7.4.  Other Evidence................................................................................    48
         7.5.  No Adverse Proceedings, Events, or Regulatory Requirements....................................    48
         7.6.  Consents, Etc.................................................................................    48
         7.7.  Opinion of Tax Counsel........................................................................    48
         7.8.  Fairness Opinion..............................................................................    48
         7.9.  Opinion of Counsel............................................................................    48
         7.10  Pooling-of-Interests Accounting...............................................................    48
         8.    Conditions Precedent to Suburban Bancshares'Obligations.......................................    49
         8.1.  Representations, Warranties, and Covenants....................................................    49
         8.2.  No Adverse Changes............................................................................    49
         8.3.  Events Preceding the Effective Date...........................................................    49
         8.4.  Other Evidence................................................................................    49
         8.5.  No Adverse Proceedings, Events, or Regulatory Requirements....................................    50
         8.6.  Consents, Etc.................................................................................    50
         8.7.  Opinion of Tax Counsel........................................................................    50
         8.8.  Fairness Opinion..............................................................................    50
         8.9.  Opinion of Counsel............................................................................    50
         9.    Terms of the Holding Company Merger...........................................................    50
         9.1.  Structure of the Holding Company Merger.......................................................    50
         9.2.  Conversion of Stock; Conversion Ratio.........................................................    51
         9.3.  Exchange Procedure............................................................................    51
         9.4.  Stock Options.................................................................................    52
</TABLE>

                                      A-4
<PAGE>

<TABLE>
<CAPTION>
         <S>                                                                                                     <C>
         9.5.  Charter of the Successor Corporation..........................................................    52
         9.6.  By-Laws of the Successor Corporation..........................................................    52
         9.7.  Anti-Dilution Provision.......................................................................    52
         9.8.  Restriction on Issuance or Repurchase of Securities...........................................    53
         10.   Terms of the Bank Merger......................................................................    53
         10.1. Structure of the Bank Merger..................................................................    53
         10.2. Conversion of Stock; Conversion Ratio.........................................................    53
         10.3. Exchange Procedure............................................................................    53
         10.4. Charter of the Successor Bank.................................................................    53
         10.5. By-Laws of the Successor Bank.................................................................    53
         10.6. Restriction on Issuance or Repurchase of Securities...........................................    53
         11.   Boards of Directors and Employment Matters....................................................    54
         12.   Amendment of this Plan........................................................................    55
         13.   Abandonment of this Plan; Effect Thereof......................................................    55
         14.   Expenses......................................................................................    57
         15.   Notices.......................................................................................    57
         16.   Entire Agreement; Effect......................................................................    57
         17.   Representations, Warranties, and Agreements...................................................    57
         18.   Governing Law.................................................................................    58
         19.   General.......................................................................................    58
</TABLE>

                                      A-5
<PAGE>

                          PLAN AND AGREEMENT TO MERGE

     PLAN AND AGREEMENT TO MERGE (this "Plan"), dated as of September 28, 1999
by and between COLUMBIA BANCORP ("Columbia Bancorp"), a Maryland corporation,
and SUBURBAN BANCSHARES, INC. ("Suburban Bancshares"), a Delaware corporation.

                             W I T N E S S E T H:

     WHEREAS, Columbia Bancorp is a bank holding company and the holder of all
of the issued and outstanding capital stock of Columbia Bank ("Columbia Bank"),
a Maryland commercial bank; and Suburban Bancshares is a bank holding company
and the holder of all of the issued and outstanding capital stock of Suburban
Bank of Maryland ("Suburban Bank"), a Maryland commercial bank; and

     WHEREAS, Columbia Bancorp desires to have Suburban Bancshares merge with
Columbia Bancorp in such a manner that, upon the merger becoming effective,
Columbia Bancorp will be the surviving Maryland corporation, and all of the
issued and outstanding shares of the Common Stock of Suburban Bancshares will be
converted into shares of the Common Stock of Columbia Bancorp, subject to the
terms and conditions and based upon Suburban Bancshares' representations,
warranties, and covenants hereinafter set forth, such merger hereinafter
referred to as the "Holding Company Merger;" and

     WHEREAS, Columbia Bancorp desires to have Suburban Bank merge with Columbia
Bank in such a manner that, upon the merger becoming effective, Columbia Bank
will be the surviving Maryland commercial bank, and all of the issued and
outstanding shares of the Common Stock of Suburban Bank will be converted into
shares of the Common Stock of Columbia Bank and owned by Columbia Bancorp,
subject to the terms and conditions and based upon Suburban Bancshares'
representations, warranties, and covenants hereinafter set forth, such merger
hereinafter referred to as the "Bank Merger," and with the Holding Company
Merger, collectively, the "Mergers;" and

     WHEREAS, Suburban Bancshares desires that it be merged with Columbia
Bancorp in the manner set forth above, and that the issued and outstanding
shares of the Common Stock of Suburban Bancshares be converted into shares of
the Common Stock of Columbia Bancorp, subject to the terms and conditions and
based upon Columbia Bancorp's representations, warranties, and covenants
hereinafter set forth; and

     WHEREAS, Suburban Bancshares desires that Suburban Bank be merged with
Columbia Bank in the manner set forth above, and that the issued and outstanding
shares of the Common Stock of Suburban Bank be converted into shares of the
Common Stock of Columbia Bank owned by Columbia Bancorp, subject to the terms
and conditions and based upon Columbia Bancorp's representations, warranties,
and covenants hereinafter set forth; and

                                      A-6
<PAGE>

     NOW, THEREFORE, in consideration of the mutual covenants and agreements
herein contained and the mutual benefits to be derived herefrom, the parties
agree as follows:

     1. Effective Date. Pursuant to Md. General Corporation Law (S) 3-113(a),
Md. Fin. Ins. Code (S) 3-709(b), and De. General Corporation Law (S) 252(c), the
effective date of this Plan and the Mergers (the "Effective Date") shall be
either (a) the first day of the month following the month in which the last of
the events in Section 2, Section 7 and Section 8 occurs; or (b) such other date
as Columbia Bancorp and Suburban Bancshares may agree upon. Columbia Bancorp and
Suburban Bancshares will prepare and execute an Agreement and Articles of Merger
in substantially the form attached as Appendix II which will set forth the
Effective Date, and will file the Agreement and Articles of Merger with the
Maryland State Department of Assessments and Taxation and the Delaware Secretary
of State. Columbia Bank and Suburban Bank will prepare and execute an Agreement
of Bank Merger in substantially the form attached as Appendix II, and will file
the Agreement of Bank Merger and the Certificate of Merger of the Commissioner
of Financial Institutions which will set forth the Effective Date with the
Maryland State Department of Assessments and Taxation.

     2. Events Preceding Effectiveness.  On or before the Effective Date the
following shall have occurred:

               (a) A majority of the Boards of Directors of each of Suburban
     Bancshares and Columbia Bancorp shall have approved and agreed to this Plan
     and the Mergers;

               (b) A majority of the Boards of Directors of each of Suburban
     Bancshares and Columbia Bancorp shall have approved and agreed to the Stock
     Option Agreements (the "Stock Option Agreements") in the forms attached as
     Appendix III and Appendix IV, respectively; and Suburban Bancshares and
     Columbia Bancorp, respectively, shall have authorized and reserved an
     adequate number of shares of its Common Stock for issuance upon exercise of
     the option granted by such Stock Option Agreements, and taken all actions
     necessary to fulfill its obligations thereunder;

               (c) the Board of Directors of Suburban Bancshares shall call a
     meeting of the stockholders of Suburban Bancshares. Notice of the time and
     place of the meeting shall be provided in accordance with De. General
     Corporation Law (S) 252(c), and this Plan and the Holding Company Merger
     shall have been ratified and confirmed by the affirmative vote of not less
     than a majority of the issued and outstanding voting stock of Suburban
     Bancshares at the meeting, in accordance with De. General Corporation Law
     (S) 252(c);

               (d) the Board of Directors of Columbia Bancorp shall call a
     meeting of the stockholders of Columbia Bancorp. Notice of the time and
     place of the meeting shall be provided in accordance with Md. General
     Corporation

                                      A-7
<PAGE>

     Law (S) 2-504, and this Plan and the Holding Company Merger shall have been
     ratified and confirmed by the affirmative vote of not less than two-thirds
     of the issued and outstanding voting stock of Columbia Bancorp at the
     meeting, in accordance with Md. General Corporation Law (S) 3-105(d);

               (e) the Board of Directors and the stockholder of Columbia Bank
     shall have approved the Bank Merger in accordance with Md. Fin. Ins. Code
     (S)(S) 3-701 et seq.;

               (f) the Board of Directors and the stockholder of Suburban Bank
     shall have approved the Bank Merger in accordance with Md. Fin. Ins. Code
     (S)(S) 3-701 et seq.;

               (g) Columbia Bancorp shall have procured the required approval,
     consent, waiver, or other administrative action with respect to this Plan
     and the transactions contemplated hereby by the Board of Governors of the
     Federal Reserve System under Section 3(a)(5) of the Bank Holding Company
     Act of 1956, as amended;

               (h) Columbia Bank and Suburban Bank shall have procured the
     required approval, consent, waiver, or other administrative action with
     respect to this Plan and the transactions contemplated hereby by the
     Maryland Commissioner of Financial Regulation under Md. Fin. Ins. Code
     (S)(S) 5-904 and 3-705;

               (i) Columbia Bank and Suburban Bank shall have procured the
     required approval, consent, waiver, or other administrative action with
     respect to this Plan and the transactions contemplated hereby by the
     Federal Deposit Insurance Corporation under Sections 18(c) and 18(d) of the
     Federal Deposit Insurance Act;

               (j) the parties shall have procured all other regulatory
     approvals, consents, waivers, or administrative actions of governmental
     entities or other persons or agencies that are necessary or appropriate to
     the consummation of the transactions contemplated by this Plan, and no
     approval, consent, waiver, or administrative action referred to in this
     Section 2(j) shall have included any condition or requirement that would
     (i) result in a materially adverse effect on Columbia Bancorp or Suburban
     Bancshares, or (ii) so materially and adversely affect the economic or
     business benefits of the Mergers that Columbia Bancorp, in the sole
     judgment of Columbia Bancorp, would not have entered into this Plan had
     such conditions or requirements been known at the date hereof;

               (k) Columbia Bancorp shall have filed a Registration Statement
     with the Securities and Exchange Commission (the "SEC") under the
     Securities

                                      A-8
<PAGE>

     Act of 1933, as amended (the "Securities Act"), pertaining to the shares of
     Common Stock of Columbia Bancorp to be issued to the stockholders of
     Suburban Bancshares pursuant to this Plan and the Holding Company Merger,
     and such Registration Statement shall have become effective and there shall
     not be in effect a stop order with respect thereto; and

                    (l) Columbia Bancorp shall have made such filings and
     obtained such approvals as are necessary under the state securities or
     "blue sky" laws pertaining to the shares of Common Stock of Columbia
     Bancorp to be issued to the stockholders of Suburban Bancshares pursuant to
     this Plan and the Mergers.

     3.   Representations and Warranties of Suburban Bancshares. Suburban
Bancshares represents and warrants to Columbia Bancorp as follows:

               3.1. Organization, Standing, and Capitalization of Suburban
Bancshares and the Suburban Subsidiaries. (a) Suburban Bancshares is a duly
organized and validly existing corporation and is in good standing under the
laws of the State of Delaware. Suburban Bancshares has the corporate power and
authority to own and hold its material properties and to carry on its business
as it is now being conducted. Suburban Bancshares is a registered bank holding
company under the Bank Holding Company Act of 1956, as amended. Suburban
Bancshares has no subsidiaries or affiliated companies and is not a party to any
joint venture or partnership other than as listed on Schedule 3.1(a)
(collectively, the "Suburban Subsidiaries").

               (b) Suburban Bank is a duly organized and validly existing
Maryland commercial bank and is in good standing under the laws of the State of
Maryland. The deposits of Suburban Bank are insured under the provisions of the
Federal Deposit Insurance Act, as amended. Each of the other Suburban
Subsidiaries is a duly organized and validly existing corporation or other
entity and is in good standing under the laws of the jurisdiction of its
incorporation or organization as set forth on Schedule 3.1(a). Each of the
Suburban Subsidiaries has the power (corporate or other) and authority to own
and hold its material properties and to carry on its business as it is now being
conducted. All outstanding shares of capital stock or other equity interests of
all of the Suburban Subsidiaries are validly issued, fully paid, and non-
assessable. Except as disclosed in Schedule 3.1(b), each of the Suburban
Subsidiaries is wholly owned by its parent. There are no outstanding options,
warrants, rights, or obligations of any kind entitling the holder thereof to
acquire shares of the capital stock or other equity interests of any of the
Suburban Subsidiaries, and there are no outstanding securities or instruments of
any kind that are convertible into shares of the capital stock or other equity
interests of any of the Suburban Subsidiaries. Except as disclosed in Schedule
3.1(b), none of the Suburban Subsidiaries is a party to any joint venture or
partnership.

               (c) Copies of all organizational documents and by-laws of
Suburban Bancshares and each of the Suburban Subsidiaries are attached as
Schedule 3.1(c), and all such copies are true and correct as of the date hereof.
The minute books of Suburban Bancshares and each of the Suburban Subsidiaries,
which have been made available to Columbia Bancorp for inspection, are

                                      A-9
<PAGE>

complete in all material respects and accurately record the actions taken by the
stockholders and directors of Suburban Bancshares and each of the Suburban
Subsidiaries.

               (d) The authorized capital stock of Suburban Bancshares consists
exclusively of 20,000,000 shares of Common Stock, par value $.01 per share,
11,301,218 of which shares are outstanding at September 17, 1999, and 1,000,000
shares of Preferred Stock, par value $.01 per share, none of which shares are
issued or outstanding. All outstanding shares of Suburban Bancshares Common
Stock are validly issued, fully paid, and non assessable. Suburban Bancshares
has reserved 500,000 shares of its Common Stock for issuance under its Stock
Option Plans. On September 17, 1999, there were outstanding options to purchase
491,134 shares of Suburban Bancshares' Common Stock at prices ranging from
$2.59375 to $5.625 pursuant to these Stock Option Plans. Except for the option
to be granted to Columbia Bancorp pursuant to the Stock Option Agreement
attached as Appendix III and as disclosed in Schedule 3.1(d), there are no other
outstanding options, warrants, rights, or obligations of any kind entitling the
holder thereof to acquire shares of the Common Stock of Suburban Bancshares, and
there are no outstanding securities or instruments of any kind that are
convertible into shares of the Common Stock of Suburban Bancshares.

               3.2. Financial Statements. Suburban Bancshares has provided in
Schedule 3.2 copies of the Consolidated Financial Statements of Suburban
Bancshares and the Suburban Subsidiaries at December 31, 1994, 1995, 1996, 1997,
and 1998 and for each of the years then ended, as reported upon by Stegman &
Company, and at June 30, 1998 and 1999 and for each of the six month periods
then ended, all of which are true and complete in all material respects, have
been prepared in accordance with generally accepted accounting principles
consistently followed throughout the periods covered by such consolidated
financial statements and present fairly the financial position, results of
operations, cash flows, and changes in stockholders' equity of Suburban
Bancshares and the Suburban Subsidiaries at the dates of and for the periods
covered by such financial statements.

               3.3. Taxes. Schedule 3.3 sets forth the tax returns to federal,
state, county, municipal, or foreign taxing authorities for the taxable year
ended December 31, 1994 and all taxable years through and including December 31,
1998 for Suburban Bancshares and the Suburban Subsidiaries. Suburban Bancshares
and the Suburban Subsidiaries have filed with appropriate federal, state,
county, municipal, or foreign taxing authorities all tax returns required to be
filed (taking any applicable extensions into consideration) and have paid or
reserved for all taxes shown to be due on such returns and all penalties and
interest payable in respect thereof. Except as disclosed in Schedule 3.3,
neither Suburban Bancshares nor any of the Suburban Subsidiaries have received
from any taxing authority any notice of deficiency or assessment of additional
taxes not paid or any notice of an intention to commence an examination or audit
of its tax returns, and no tax audits by any taxing authority are in process.
Except as disclosed on Schedule 3.3, neither Suburban Bancshares nor any of the
Suburban Subsidiaries have granted any waiver of any statute of limitations or
otherwise agreed to any extension of a period for the assessment of any federal,
state, county, municipal, or foreign income tax. The accruals and reserves
reflected in the consolidated financial statements which Suburban Bancshares has

                                     A-10
<PAGE>

provided to Columbia Bancorp as described in Section 3.2 are adequate to cover
all taxes (including interest and penalties, if any, thereon) that are payable
or accrued as a result of the operations of Suburban Bancshares and the Suburban
Subsidiaries for all periods prior to the date of such consolidated financial
statements. For purposes of this Section 3.3, any reference to the Suburban
Subsidiaries shall be deemed to include any entity listed on Schedules 3.1(a)
and 3.1 (b).

               3.4. No Undisclosed Liabilities. Except as and to the extent
reflected or reserved against in the consolidated financial statements referred
to in Section 3.2, neither Suburban Bancshares nor any of the Suburban
Subsidiaries at the dates of such consolidated financial statements had any
material liabilities or obligations (whether accrued, absolute, or contingent)
required under generally accepted accounting principles to be reflected thereon
which would materially and adversely affect the fair presentation of such
financial statements. Neither Suburban Bancshares nor any of the Suburban
Subsidiaries has incurred any liability since the date of the consolidated
financial statements referred to in Section 3.2 (including any liability for
taxes) which would materially and adversely affect the condition (financial or
otherwise), assets, liabilities, business, or operations of Suburban Bancshares
and the Suburban Subsidiaries, taken as a whole, other than liabilities which
have been incurred in the ordinary course of business.

               3.5. Absence of Certain Changes or Events. Except as set forth in
Schedule 3.5, since December 31, 1998 there has not been:

                    (a) Any materially adverse change in the financial position,
     results of operations, assets, liabilities, or business of Suburban
     Bancshares or the Suburban Subsidiaries, other than changes in the ordinary
     course of business;

                    (b) any increase in salaries or wages of directors,
     officers, or employees of Suburban Bancshares or the Suburban Subsidiaries
     other than in the ordinary course of business; or any establishment or
     increase of any employment, compensation, bonus, pension, option, incentive
     or deferred compensation, retirement payments, profit sharing, or similar
     agreement or benefit, authorized, granted, or accrued to any directors,
     officers, or employees of Suburban Bancshares or the Suburban Subsidiaries
     other than in the ordinary course of business; or

                    (c) any declaration, payment, or set aside by Suburban
     Bancshares of any dividend or distribution in respect of its Common Stock,
     or any purchase, issuance, or sale of any of its Common Stock.

               3.6. Complete and Accurate Disclosure. Neither this Plan (insofar
as it relates to Suburban Bancshares and the Suburban Subsidiaries, the Common
Stock of Suburban Bancshares, and the involvement of Suburban Bancshares in the
transactions contemplated hereby) nor any financial statement, schedule,
certificate, or other statement or document set

                                     A-11
<PAGE>

forth on a schedule delivered by Suburban Bancshares to Columbia Bancorp in
connection with this Plan, when considered in the aggregate, contains any
statement which, at the time and in light of the circumstances under which it is
made, is false or misleading with respect to any material fact or omits to state
any material fact necessary to make the statements contained herein or therein
not false or misleading.

               3.7. Title to Properties; Absence of Liens and Encumbrances;
Compliance with Laws. Except as disclosed on Schedule 3.7, Suburban Bancshares
and each of the Suburban Subsidiaries has good and marketable title to all of
their respective properties and assets, including those reflected in the
consolidated financial statements referred to in Section 3.2, except as sold or
otherwise disposed of for fair value and only in the ordinary course of
business, free and clear of all liens and encumbrances, except (i) with respect
to property as to which they are lessees, (ii) with respect to real estate owned
by Suburban Bancshares or the Suburban Subsidiaries, for use, occupancy, and
similar restrictions of public record that may be observed by an inspection of
the property, and such other utility and other easements and encumbrances as do
not materially adversely affect the fair market value of such real property, and
(iii) liens to secure borrowings, liens to secure governmental deposits, and
liens for current taxes not yet due and payable. Neither Suburban Bancshares nor
any of the Suburban Subsidiaries owns or leases real property except as
disclosed on Schedule 3.7, and is not in default under any material lease of
real or personal property to which it is a party. As of the date hereof, except
as disclosed on Schedule 3.7, the real properties, structures, buildings,
equipment, and the tangible personal property owned, operated, or leased by
Suburban Bancshares or any of the Suburban Subsidiaries are (x) in good repair,
order, and condition, except for depletion, depreciation, and ordinary wear and
tear, (y) suitable for the uses for which they were intended, and (z) free from
any known structural defects. As of the date hereof, there are no laws,
conditions of record, or other impediments which materially interfere with the
intended uses by Suburban Bancshares or any of the Suburban Subsidiaries of the
real property or tangible personal property owned or leased by it, except as set
forth in Schedule 3.7. Neither Suburban Bancshares nor any of the Suburban
Subsidiaries have received any notice of any violation of any applicable law,
building code, zoning ordinance, or other similar law. Suburban Bancshares and
the Suburban Subsidiaries own or have the rights to use all real and personal
properties and assets that are material to the conduct of the business as now
conducted of Suburban Bancshares and the Suburban Subsidiaries, taken as a
whole.

               3.8. Contracts. Except for the plans, contracts, and agreements
of Suburban Bancshares and the Suburban Subsidiaries (or of any plan under
Section 3.8(b)) disclosed on Schedule 3.8, neither Suburban Bancshares nor any
of the Suburban Subsidiaries (nor any plan under Section 3.8(b)) is a party to
or subject to:

                    (a) Any employment, consultation, or compensation contract
      or arrangement (other than those terminable at will) with any officer,
      consultant, director, or employee;

                                     A-12
<PAGE>

                    (b) any plan, contract, program, understanding, or agreement
     providing for bonuses, pensions, severance pay, executive compensation,
     options, stock purchases, or any other form of retirement, incentive or
     deferred compensation, retirement payments, death benefits, profit sharing,
     branch closing benefits, workers' compensation, tuition reimbursement or
     scholarship program, any plans providing benefits or payments in the event
     of a change in control, change in ownership, or sale of a substantial
     portion (including all or substantially all) of the assets of Suburban
     Bancshares or any of the Suburban Subsidiaries, or any health, accident,
     disability, sick leave, vacation pay, life insurance, or other welfare
     benefit, or any other employee or retired employee benefit (including,
     without limitation, any "employee benefit plan" as defined in Section 3(3)
     of the Employee Retirement Income Security Act of 1974, as amended
     ("ERISA")) in which any current or former employee, director, or agent (or
     beneficiary of any of them) of Suburban Bancshares or any of the Suburban
     Subsidiaries is or was, within the last six years, entitled to participate;

                    (c)  any contract or agreement with any labor union;

                    (d)  any lease of real or personal property with annual
     rentals in excess of $5,000;

                    (e)  any agreement for services in excess of $10,000 per
     year or for the purchase or disposition of any equipment or supplies except
     individual purchase orders for office supplies incurred in the ordinary
     course of business of $10,000 or less;

                    (f)  any instrument evidencing or relating to indebtedness
     for borrowed money except for customer accounts, deposits, certificates of
     deposit, federal funds purchased, and the like which may be construed as
     borrowings and except for loans made by Suburban Bank as lender in the
     ordinary course of its business;

                    (g)  any lease or other contract containing covenants not to
     enter into or consummate the transactions contemplated hereby or which
     provides for payments in excess of $2,000 and will be terminated or
     violated by the Mergers or in respect of which the Mergers would cause a
     default or acceleration of obligations; or

                    (h)  any other contract or agreement not of the type covered
     by any of the other specific terms of this Section 3.8 obligating Suburban
     Bancshares or any Suburban Subsidiary to expenditures in excess of $25,000.

Each of the instruments disclosed on Schedule 3.8 is valid and in full force and
effect.  Neither Suburban Bancshares nor any of the Suburban Subsidiaries are in
default nor have any of them

                                     A-13
<PAGE>

received any notice that they are in default, nor to their actual knowledge is
any other party in default, under any material agreements, instruments, or
obligations to which Suburban Bancshares or any of the Suburban Subsidiaries is
a party or by which they are bound.

               3.9. Litigation, Etc. Except as disclosed on Schedule 3.9, (a)
there is no litigation, proceeding, or investigation pending or, to the
knowledge of Suburban Bancshares, threatened against Suburban Bancshares or any
of the Suburban Subsidiaries which would result in any materially adverse change
in the condition (financial or otherwise), assets, liabilities, business,
operations, or future prospects of Suburban Bancshares and the Suburban
Subsidiaries, taken as a whole; (b) there are no outstanding orders, writs,
injunctions, judgments, decrees, directives, consent agreements, or memoranda of
understanding issued by any federal, state, or local court or governmental
authority or arbitration tribunal issued against or with the consent of Suburban
Bancshares or any of the Suburban Subsidiaries that materially and adversely
affect the condition (financial or otherwise), assets, liabilities, business,
operations, or future prospects or that in any manner restrict Suburban
Bancshares' right to carry on its business or that of the Suburban Subsidiaries
as now conducted; and (c) Suburban Bancshares is aware of no fact or condition
now existing that might give rise to any litigation, investigation, or
proceeding which, if determined adversely to Suburban Bancshares or any of the
Suburban Subsidiaries, would materially and adversely affect the condition
(financial or otherwise), assets, liabilities, business, operations, or future
prospects of Suburban Bancshares and the Suburban Subsidiaries, taken as a
whole, or would restrict in any manner Suburban Bancshares' right to carry on
its business or that of the Suburban Subsidiaries as now conducted. Suburban
Bancshares has disclosed on Schedule 3.9 all litigation in which Suburban
Bancshares or any of the Suburban Subsidiaries is involved as a party (other
than bankruptcy proceedings in which Suburban Bancshares or any of the Suburban
Subsidiaries has filed proofs of claim or routine collection and foreclosure
suits initiated in the ordinary course of business).

               3.10.Environmental Matters. (a) The following terms shall have
the indicated meaning:

                     "Property" or "Properties" means all branch properties now
     or formerly owned or operated, all other real property now owned or
     operated, and any real properties owned or operated on or after July 1,
     1991 and subsequently disposed of.

                     "Environmental Law" means (i) any applicable federal,
     state, or local statute, law, ordinance, rule, regulation, code, license,
     permit, authorization, approval, consent, order, judgment, decree,
     directive, requirement, or agreement with any court, governmental
     authority, or other regulatory or administrative agency or commission,
     domestic or foreign ("Governmental Entity") now existing, relating to the
     use, storage, treatment, generation, transportation, processing, handling,
     labeling, production, release, or disposal of Hazardous Substances, each as
     amended, or (ii) any common law that may impose liability or

                                     A-14
<PAGE>

     obligations for injuries or damages due to the presence of or exposure to
     any Hazardous Substance.

               "Hazardous Substance" means any substance, whether liquid, solid,
     or gas, listed, defined, designated, or classified as hazardous, toxic,
     radioactive, or dangerous under any applicable Environmental Law, whether
     by type or by quantity. Hazardous Substance includes, without limitation,
     any "hazardous substance" as defined in the Comprehensive Environmental
     Response, Compensation and Liability Act, as amended, and any other
     substance regulated or subject to any federal environmental statute,
     including, but not limited to the Toxic Substance Control Act, Clean Water
     Act, Clean Air Act, Oil Pollution Act and Resource Conservation and
     Recovery Act, or a similar state statute, regardless of the amount of the
     Hazardous Substance.

          (b) Except as disclosed on Schedule 3.10 or as would not individually
or in the aggregate have a materially adverse effect on the condition (financial
or otherwise), assets, liabilities, business, or operations of Suburban
Bancshares and the Suburban Subsidiaries, taken as a whole:

               (i) neither Suburban Bancshares nor any of the Suburban
     Subsidiaries has received any written notices, demand letters, or written
     requests for information from any Governmental Entity or any third party
     indicating that Suburban Bancshares or any Suburban Subsidiary may be in
     violation of, or liable under, any Environmental Law;

               (ii) there are no civil, criminal, or administrative actions,
     suits, demands, claims, hearings, investigations, or proceedings pending or
     to the knowledge of Suburban Bancshares threatened against Suburban
     Bancshares or any Suburban Subsidiary alleging that they may be in
     violation of, or liable under, any Environmental Law;

               (iii) no reports have been filed with any Governmental Entity,
     nor to the knowledge of Suburban Bancshares are any reports required to be
     filed with any Governmental Entity, by Suburban Bancshares or any of the
     Suburban Subsidiaries concerning the release of any Hazardous Substance or
     the violation of any Environmental Law on or at any of the Properties of
     Suburban Bancshares or any of the Suburban Subsidiaries;

               (iv) to the knowledge of Suburban Bancshares or except as
     disclosed on Schedule 3.10, there are no underground storage tanks on, in,
     or under any of the Properties of Suburban Bancshares or any of the
     Suburban Subsidiaries, and no underground storage tanks have been closed or
     removed from any Property of Suburban Bancshares or any of the Suburban
     Subsidiaries while

                                     A-15
<PAGE>

     such Property was owned or operated by Suburban Bancshares or any of the
     Suburban Subsidiaries;

               (v) to the knowledge of Suburban Bancshares or except as
     disclosed on Schedule 3.10, no Hazardous Substance has been generated,
     used, stored, processed, disposed of, or discharged on or into any of the
     Properties of Suburban Bancshares or any of the Suburban Subsidiaries,
     except for such hazardous substances as may be used in the everyday
     business of a bank office; and

               (vi) to the knowledge of Suburban Bancshares or except as
     disclosed on Schedule 3.10, no materials containing asbestos have been used
     or incorporated in any building or other structure or improvement located
     on any of the Properties of Suburban Bancshares or any of the Suburban
     Subsidiaries.

         (c) There are no permits or licenses or agency filings or reports
required under any Environmental Law in respect of any of the Properties now or
formerly owned or operated by Suburban Bancshares or any of the Suburban
Subsidiaries that the absence of which could, individually or in the aggregate,
have a materially adverse effect on the condition (financial or otherwise),
assets, liabilities, business, or operations of Suburban Bancshares and the
Suburban Subsidiaries, taken as a whole.

         (d) Suburban Bancshares has disclosed on Schedule 3.10 a copy of its
current policy regarding compliance with Environmental Laws.

         3.11. Labor Matters. To Suburban Bancshares' knowledge, no organization
effort with respect to any of the employees of Suburban Bancshares or any of the
Suburban Subsidiaries is pending or threatened, and no labor dispute, strike,
work stoppage, employee action, or labor relation problem which may materially
affect Suburban Bancshares or any of the Suburban Subsidiaries currently is
pending or threatened. Suburban Bancshares and each of the Suburban Subsidiaries
have at all times in all material respects complied with all applicable employee
termination notice and similar laws. Suburban Bancshares and each of the
Suburban Subsidiaries have at all times complied in all material respects with
all applicable family medical leave and similar laws. If applicable, Suburban
Bancshares and each of the Suburban Subsidiaries have at all times complied in
all material respects with all applicable requirements of the Worker Adjustment
and Retraining Notification Act and all similar state laws.

         3.12. Pension and Welfare Matters. With respect to the plans,
contracts, programs, understandings, or agreements identified pursuant to
Sections 3.8(a) and (b) (for purposes of this Section 3.12, the "plans"):

               (a) Schedule 3.12 clearly identifies all of the plans which are
     (i) Multiemployer Plans (as defined in (l) below), (ii) multiple employer
     plans subject to Sections 4063 and 4064 of ERISA ("Multiple Employer
     Plans"), (iii)

                                     A-16
<PAGE>

     plans other than Multiemployer Plans and Multiple Employer Plans that are
     subject to Section 412 of the Internal Revenue Code of 1986, as amended
     (the "Code"), (iv) plans intended to qualify under Section 401 of the Code,
     and (v) "welfare benefit plans" within the meaning of Section 3(1) of ERISA
     which provide for continuing benefits or coverage for any participant or
     any beneficiary of a participant after such participant's termination of
     employment except coverage or benefits required by Section 4980B of the
     Code if paid 100% by the participant;

               (b) true, correct and complete copies of the following documents,
     with respect to each of the plans have been made available or delivered to
     Columbia Bancorp: (i) all plan documents, including trust agreements,
     insurance policies, loan documents, and service agreements and amendments
     thereto, (ii) the most recent Forms 5500 and any financial statements
     attached thereto and those for the prior three years, (iii) the last
     Internal Revenue Service determination letter and the application with
     respect thereto, (iv) summary plan descriptions, (v) the most recent
     actuarial statements and those for the prior three years, (vi) written
     descriptions of all non-written agreements relating to any such plan, as
     applicable, for Suburban Bancshares and each of the Suburban Subsidiaries,
     and (vii) all filings with a governmental agency or entity within the last
     three years, including, without limitation, filings under the voluntary or
     other compliance programs of the U.S. Department of Labor or the Internal
     Revenue Service;

               (c) each of the plans has been operated in all material respects
     in accordance with its terms and in accordance with all applicable laws
     including, but not limited to, the ERISA, the Code, the Consolidated
     Omnibus Budget Reconciliation Act of 1985, the Health Insurance Portability
     and Accountability Act of 1996, and state health care continuation laws;

               (d) all reporting and disclosure requirements of ERISA imposed
     upon each such plan have been complied with in all material respects, and
     all required governmental filings have been made with respect to the plans;

               (e) none of (i) the plans, (ii) the Suburban Subsidiaries, and
     (iii) Suburban Bancshares, and to Suburban Bancshares' knowledge, (x) no
     current or former director, officer, employee, agent, or representative of
     Suburban Bancshares or any of the Suburban Subsidiaries, and (y) no
     fiduciary, "party in interest" (as defined in Section 3(14) of ERISA) or
     "disqualified person" (as defined in Section 4975 of the Code) with respect
     to any of the plans has engaged in any non-exempt "prohibited transaction"
     in connection with any of the plans within the meaning of Section 4975 of
     the Code or Title I, Part 4 of ERISA;

               (f) none of the plans has any accumulated funding deficiency (as
     defined in Section 302 of ERISA and Section 412 of the Code), whether or
     not

                                      A-17
<PAGE>

     waived, with respect to the latest five plan years, nor any liability to
     the Pension Benefit Guaranty Corporation (the "PBGC") (other than normal
     premium payments);

               (g) with respect to plans which are pension plans (as defined in
     Section 3(2) of ERISA) subject to Title IV of ERISA, the assets of each
     such funded plans equal or exceed the liabilities (as defined in Section
     4001(a)(16) of ERISA) under such plans when such liabilities are valued on
     a termination basis using PBGC interest and other assumptions;

               (h) no contributions to any of the plans from Suburban Bancshares
     or any of the Suburban Subsidiaries are currently past due and, if
     applicable, all past service and other liabilities currently existing but
     payable in the future, if any, are reflected in the latest actuarial report
     in accordance with sound actuarial principles;

               (i) no audits, proceedings, investigations, filings, or other
     matters (excluding any determination letter application that has been or
     may be filed prior to the Effective Date) are pending before the IRS, the
     Department of Labor, the PBGC, or other public or quasi-public body in
     connection with any such plans;

               (j) each plan intended to qualify under Section 401(a) of the
     Code is so qualified and the trust maintained pursuant thereto is exempt
     from taxation under Section 501 of the Code and nothing has occurred with
     respect to the operation or administration of such plan which would cause
     the loss of such qualification or exemption or the imposition of any
     liability, penalty, or tax under ERISA or the Code that could reasonably be
     expected to have a material adverse effect on the condition (financial or
     otherwise), assets, liabilities, business, or operations of Suburban
     Bancshares and the Suburban Subsidiaries, taken as a whole, or on such
     plan;

               (k) except as disclosed in Schedule 3.12, through the Effective
     Date, there will be no changes in the operation of the plans or in the
     documents constituting or affecting the plans except for amendments and
     operational changes required by applicable law which do not materially
     increase the cost of such plans;

               (l) no employees, former employees, or retired employees of
     Suburban Bancshares or any of the Suburban Subsidiaries, as a result of
     their employment with Suburban Bancshares or any of the Suburban
     Subsidiaries, are participants in any "multiemployer plan" which is a
     "pension plan," as such terms are defined in Sections 3(37) and 3(2) of
     ERISA, respectively, ("Multiemployer Plan") and neither Suburban Bancshares
     nor any of the Suburban Subsidiaries has any current, contingent or
     potential liability with respect to any such plan;

                                      A-18
<PAGE>

               (m) no "reportable event," as such term is defined in Section
     4043(c) of ERISA, has occurred with respect to any plan since the effective
     date of ERISA, other than a reportable event for which the 30 days notice
     requirement under regulations of the PBGC has been waived;

               (n) there are no pending or threatened claims by or disputes with
     any participants or beneficiaries of the plans, except plan benefit claims
     arising in the normal course of the operations of the plans (other than
     terminated plans) and as to which no dispute exists;

               (o) Suburban Bancshares has no knowledge of any facts which could
     give rise to any claims against any plan or any fiduciary of any plan,
     except for plan benefit claims arising in the normal course of the
     operations of the plans (other than terminated plans);

               (p) neither Suburban Bancshares nor any of the Suburban
     Subsidiaries nor any fiduciary of any plan has given notice to any
     fiduciary liability insurer of any claims or potential claims in connection
     with any of the plans;

               (q) except as disclosed in Schedule 3.12, each of the plans which
     benefit retired employees of Suburban Bancshares or any of the Suburban
     Subsidiaries may effectively be terminated or amended, in any manner and at
     any time, without further liability to its participants, by its sponsoring
     employer;

               (r) neither Suburban Bancshares nor any of the Suburban
     Subsidiaries has provided, nor is required to provide, security to any
     pension plan or to any single-employer plan pursuant to Section 401(a)(29)
     of the Code or Section 307 of ERISA;

               (s) there has been no announcement or legally binding commitment
     by Suburban Bancshares or any of the Suburban Subsidiaries to create an
     additional plan, or to amend a plan except for amendments required by
     applicable law which do not materially increase the cost of such plan;

               (t) as to any terminated plans, all obligations for plan benefits
     or other liabilities have been satisfied in full;

               (u) none of the plans contains any provision which would prohibit
     the transactions contemplated by this Plan or which, except as disclosed in
     Schedule 3.12, would give rise to any severance, termination, or other
     payments or liabilities, or any forgiveness of indebtedness, vesting,
     distribution, increase in benefits, or obligations to fund benefits as a
     result of the transactions contemplated by this Plan; no payment that is
     owed or may become due any
                                      A-19
<PAGE>

     director, officer, employee, or agent of Suburban Bancshares or any of the
     Suburban Subsidiaries in connection with a plan will be non-deductible to
     the payor under Section 280G of the Code, and none of the Suburban
     Subsidiaries, Columbia Subsidiaries, Suburban Bancshares, and Columbia
     Bancorp will be required to "gross up" or otherwise compensate any person
     in connection with a plan because of the imposition of any excise tax under
     Section 4999 of the Code; and

               (v) no plan is funded by, associated with, or related to a
     "voluntary employees' beneficiary association" within the meaning of
     Section 501(c)(9) of the Code.

        3.13. Related Party Transactions. Except as disclosed on Schedule 3.13,
neither Suburban Bancshares nor any of the Suburban Subsidiaries has any
contract, extension of credit, business arrangement, or other relationship of
any kind with any of the following persons: (a) any executive officer or
director of Suburban Bancshares or any of the Suburban Subsidiaries; (b) any
stockholder owning five percent or more of the outstanding Common Stock of
Suburban Bancshares; or (c) any "affiliate" (as defined in the SEC Rule 405) of
the foregoing persons or any business in which any of the foregoing persons is
an officer, director, employee, or five percent or greater equity owner.

        3.14. No Conflict with Other Documents. Except as disclosed on Schedule
3.14, neither the execution and delivery of this Plan nor the carrying out of
the transactions contemplated hereunder will result in any violation,
termination, or default or acceleration of, or be in conflict with, any terms of
any contract or other instrument to which Suburban Bancshares or any of the
Suburban Subsidiaries is a party, or of any judgment, decree, or order
applicable to Suburban Bancshares or any of the Suburban Subsidiaries, or result
in the creation of any lien, charge, or encumbrance upon any of their properties
or assets, except for any of the foregoing which would not have a material
adverse effect upon the condition (financial or otherwise), assets, liabilities,
business, or operations of Suburban Bancshares and the Suburban Subsidiaries,
taken as a whole.

        3.15. Compliance with Laws; Governmental Authorizations. (a) Except
where noncompliance would not have a material and adverse effect upon the
condition (financial or otherwise), assets, liabilities, business, or operations
of Suburban Bancshares and the Suburban Subsidiaries, taken as a whole, (i)
Suburban Bancshares and each of the Suburban Subsidiaries are in compliance with
all statutes, laws, ordinances, rules, regulations, judgments, orders, decrees,
directives, consent agreements, memoranda of understanding, permits,
concessions, grants franchises, licenses, and other governmental authorizations
or approvals applicable to Suburban Bancshares, the Suburban Subsidiaries, or
any of their properties; and (ii) all permits, concessions, grants, franchises,
licenses, and other governmental authorizations and approvals necessary for the
conduct of the business of Suburban Bancshares and the Suburban Subsidiaries as
now conducted have been duly obtained and are in full force and effect, and
there

                                      A-20
<PAGE>

are no proceedings pending or, to Suburban Bancshares' knowledge, threatened
which may result in the revocation, cancellation, suspension, or materially
adverse modification of any thereof.

        (b) Suburban Bancshares has filed all reports that it was required to
file with the SEC under the Securities Exchange Act of 1934, as amended (the
"Exchange Act"), all of which complied in all material respects with all
applicable requirements of the Exchange Act and the rules and regulations
adopted thereunder. As of their respective dates, each such report, statement,
form, or other document, including without limitation, any financial statements
or schedules included therein, did not contain any untrue statement of a
material fact or omit to state a material fact required to be stated therein or
necessary to make the statements therein, in light of the circumstances under
which they were made, not misleading, provided, that information as of a later
date shall be deemed to modify information as of an earlier date.

        3.16. Authority; Enforceability. The execution, delivery, and
performance of this Plan by Suburban Bancshares have been duly and validly
authorized by its Board of Directors, subject only to requisite approval by the
stockholders of Suburban Bancshares and appropriate governmental regulatory
authorities. This Plan is a valid and binding agreement of Suburban Bancshares,
enforceable against it in accordance with its terms, subject as to enforcement
to bankruptcy, insolvency, fraudulent transfer, reorganization, moratorium, and
similar laws of general applicability relating to or affecting creditors' rights
and to general equity principles.

        3.17. Insurance. All insurance policies held by Suburban Bancshares and
the Suburban Subsidiaries relating to their operations (except for title
insurance policies), including without limitation all financial institutions
bonds, are set forth on Schedule 3.17. All such policies are in full force and
effect. Neither Suburban Bancshares nor any of the Suburban Subsidiaries has
received any notice of cancellation with respect to any such policies and has no
reason to expect that it will receive a notice of cancellation from any of its
present insurance carriers; provided, however, that Suburban Bancshares makes no
representation as to the effect of this Plan or the Mergers on its present
financial institutions bond or bonds.

        3.18. Financial Institutions Bond. Since January 1, 1993, Suburban
Bancshares and the Suburban Subsidiaries have continuously maintained in full
force and effect one or more financial institutions bonds insuring Suburban
Bancshares and the Suburban Subsidiaries against acts of dishonesty by each of
their employees. No claim has been made under any such bond since such date, and
Suburban Bancshares is not aware of any fact or condition now existing which
forms the basis of a claim under any such bond. Suburban Bancshares and the
Suburban Subsidiaries have no reason to expect that their present financial
institutions bond or bonds will not be renewed by their carrier on substantially
the same terms as those now in effect; provided, however, that Suburban
Bancshares makes no representation as to the effect of this Plan or the Mergers
on its present financial institutions bond or bonds.

        3.19. Brokers; Financial Advisor. All negotiations relating to this Plan
and the transactions contemplated hereunder have been carried on by Suburban
Bancshares directly or

                                      A-21
<PAGE>

through its counsel or financial advisor, and there has been no intervention of
any person as the result of any action of Suburban Bancshares (and, so far as
known to Suburban Bancshares, no intervention of any other person) in such
manner as to give rise to any valid claim against any of the parties hereto for
a brokerage commission, finder's fee, or other like payment (other than to its
financial advisor, Danielson Associates Inc.). Schedule 3.19 is a copy of the
agreement with Danielson Associates Inc., which has been engaged by Suburban
Bancshares as its financial advisor and to deliver an opinion as to the fairness
of the transactions contemplated by this Plan to Suburban Bancshares.

        3.20. Beneficial Ownership of Columbia Bancorp Common Stock. As of the
date hereof, Suburban Bancshares does not beneficially own any shares of
Columbia Bancorp Common Stock or have any option, warrant, or right of any kind
to acquire the beneficial ownership of any Columbia Bancorp Common Stock, except
pursuant to the terms of this Plan, the terms of the Stock Option Agreement
attached as Appendix IV, or in a fiduciary capacity.

        3.21. Year 2000. Suburban Bancshares has carried out a review to
evaluate the extent to which the business or operations of Suburban Bancshares
or any of the Suburban Subsidiaries will be affected by the Year 2000 Problem
(as defined below). As a result of such review, Suburban Bancshares has no
reason to believe, and does not believe, that the Year 2000 Problem will have a
material adverse effect on the condition (financial or otherwise), assets,
liabilities, business, or operations of Suburban Bancshares and the Suburban
Subsidiaries, taken as a whole. Suburban Bancshares reasonably believes that the
suppliers, vendors, customers or other material third parties used or served by
Suburban Bancshares and the Suburban Subsidiaries are addressing or will address
the Year 2000 Problem in a timely manner. Suburban Bancshares is in compliance
with all applicable requirements of any Governmental Entity relating to the Year
2000 Problem and has not received any correspondence from or provided any
written information to any Governmental Entity relating to the Year 2000 Problem
except as disclosed in Schedule 3.21. Suburban Bancshares has provided in
Schedule 3.21 copies of all of its internal plans, including estimates of the
anticipated associated costs, for addressing the Year 2000 Problem as it relates
to Suburban Bancshares and the Suburban Subsidiaries. "Year 2000 Problem" means
the risk that computer hardware or software applications will not record, store,
process, calculate and present calendar dates falling on and after January 1,
2000, and calculate information dependent upon or relating to such dates, in the
same manner and with the same functionality, data integrity and performance as
such products record, store, process, calculate and present calendar dates
falling on or before December 31, 1999, and calculate information dependent on
or relating to such dates.

     4. Representations and Warranties of Columbia Bancorp. Columbia Bancorp
represents and warrants to Suburban Bancshares as follows:

          4.1. Organization, Standing, and Capitalization of Columbia Bancorp
and Columbia Subsidiaries. (a) Columbia Bancorp is a duly organized and validly
existing corporation in good standing under the laws of the State of Maryland.
Columbia Bancorp has the corporate power and authority to own and hold its
properties and to carry on its business as it is
                                      A-22
<PAGE>

now being conducted. Columbia Bancorp is a registered bank holding company under
the Bank Holding Company Act of 1956, as amended. Columbia Bancorp has no
subsidiaries or affiliated companies and is not a party to any joint venture or
partnership other than as listed on Schedule 4.1(a) (collectively, the "Columbia
Subsidiaries").

        (b) Columbia Bank is a duly organized and validly existing Maryland
commercial bank and is in good standing under the laws of the State of Maryland.
The deposits of Columbia Bank are insured under the provisions of the Federal
Deposit Insurance Act, as amended. Each of the other Columbia Subsidiaries is a
duly organized and validly existing corporation or other entity and is in good
standing under the laws of the jurisdiction of its incorporation or organization
as set forth on Schedule 4.1(a). Each of the Columbia Subsidiaries has the power
(corporate or other) and authority to own and hold its material properties and
to carry on its business as it is now being conducted. All outstanding shares of
capital stock or other equity interests of all of the Columbia Subsidiaries are
validly issued, fully paid, and non-assessable. Except as disclosed in Schedule
4.1(b), each of the Columbia Subsidiaries is wholly owned by its parent. There
are no outstanding options, warrants, rights, or obligations of any kind
entitling the holder thereof to acquire shares of the capital stock or other
equity interests of any of the Columbia Subsidiaries, and there are no
outstanding securities or instruments of any kind that are convertible into
shares of the capital stock or other equity interests of any of the Columbia
Subsidiaries. Except as disclosed in Schedule 4.1(b), none of the Columbia
Subsidiaries is a party to any joint venture or partnership.

        (c) Copies of all organization documents and by-laws of Columbia Bancorp
and each of the Columbia Subsidiaries are attached as Schedule 4.1(c), and all
such copies are true and correct as of the date hereof. The minute books of
Columbia Bancorp and each of the Columbia Subsidiaries, which have been made
available to Suburban Bancshares for inspection, are complete in all material
respects and accurately record the actions taken by the stockholders and
directors of Columbia Bancorp and each of the Columbia Subsidiaries.

        (d) The authorized capital stock of Columbia Bancorp consists
exclusively of 9,994,000 shares of Common Stock, par value $.01 per share,
4,506,035 of which shares are outstanding on September 17, 1999, and 6,000
shares of Series A Convertible Preferred Stock, par value $.01 per share, none
of which shares are outstanding on September 17, 1999. All outstanding shares of
Columbia Bancorp Common Stock are validly issued, fully paid, and non-
assessable. Columbia Bancorp has reserved 300,000 shares of its Common Stock for
issuance under its Dividend Reinvestment and Stock Purchase Plan and 300,000
shares of its Common Stock for issuance under its Stock Option Plans. On
September 17, 1999, there were outstanding options to purchase 292,310 shares of
Columbia Bancorp's Common Stock at prices ranging from $4.545 to $17.00 pursuant
to these Stock Option Plans. Except for the option to be granted to Suburban
Bancshares pursuant to the Stock Option Agreement attached as Appendix IV and as
disclosed in Schedule 4.1(d), there are no other outstanding options, warrants,
rights, or obligations of any kind entitling the holder thereof to acquire
shares of the Common Stock of Columbia Bancorp, and there are no outstanding
securities or instruments of any kind that are convertible into shares of the
Common Stock of Columbia Bancorp. The Common Stock of

                                      A-23
<PAGE>

Columbia Bancorp deliverable pursuant to this Plan will be, prior to its
issuance, duly authorized for issuance and will, when issued and delivered in
accordance with this Plan, be duly and validly issued, fully paid, and
nonassessable.

        4.2. Financial Statements. Columbia Bancorp has provided in Schedule 4.2
copies of the Consolidated Financial Statements of Columbia Bancorp and the
Columbia Subsidiaries at December 31, 1994, 1995, 1996, 1997, and 1998 and for
each of the years then ended, as reported upon by KPMG LLP, and at June 30, 1998
and 1999 and for each of the six month periods then ended, all of which are true
and complete in all material respects, have been prepared in accordance with
generally accepted accounting principles consistently followed throughout the
periods covered by such consolidated financial statements and present fairly the
financial position, results of operations, cash flows, and changes in
stockholders' equity of Columbia Bancorp and the Columbia Subsidiaries at the
dates of and for the periods covered by such financial statements.

        4.3. Taxes. Schedule 4.3 sets forth the tax returns to federal, state,
county, municipal, or foreign taxing authorities for the taxable year ended
December 31, 1994 and all taxable years through and including December 31, 1998
for Columbia Bancorp and the Columbia Subsidiaries. Columbia Bancorp and the
Columbia Subsidiaries have filed with appropriate federal, state, county,
municipal, or foreign taxing authorities all tax returns required to be filed
(taking any applicable extensions into consideration) and have paid or reserved
for all taxes shown to be due on such returns and all penalties and interest
payable in respect thereof. Except as disclosed in Schedule 4.3, neither
Columbia Bancorp nor any of the Columbia Subsidiaries have received from any
taxing authority any notice of deficiency or assessment of additional taxes not
paid or any notice of an intention to commence an examination or audit of its
tax returns, and no tax audits by any taxing authority are in process. Except as
disclosed on Schedule 4.3, neither Columbia Bancorp nor any of the Columbia
Subsidiaries have granted any waiver of any statute of limitations or otherwise
agreed to any extension of a period for the assessment of any federal, state,
county, municipal, or foreign income tax. The accruals and reserves reflected in
the consolidated financial statements which Columbia Bancorp has provided to
Suburban Bancshares as described in Section 4.2 are adequate to cover all taxes
(including interest and penalties, if any, thereon) that are payable or accrued
as a result of the operations of Columbia Bancorp and the Columbia Subsidiaries
for all periods prior to the date of such consolidated financial statements. For
purposes of this Section 4.3, any reference to the Columbia Subsidiaries shall
be deemed to include any entity listed on Schedules 4.1(a) and 4.1 (b).

        4.4. No Undisclosed Liabilities. Except as and to the extent reflected
or reserved against in the consolidated financial statements referred to in
Section 4.2, neither Columbia Bancorp nor any of the Columbia Subsidiaries at
the dates of such consolidated financial statements had any material liabilities
or obligations (whether accrued, absolute, or contingent) required under
generally accepted accounting principles to be reflected thereon which would
materially and adversely affect the fair presentation of such financial
statements. Neither Columbia Bancorp nor any of the Columbia Subsidiaries has
incurred any liability since

                                      A-24
<PAGE>

the date of the consolidated financial statements referred to in Section 4.2
(including any liability for taxes) which would materially and adversely affect
the condition (financial or otherwise), assets, liabilities, business, or
operations of Columbia Bancorp and the Columbia Subsidiaries, taken as a whole,
other than liabilities which have been reasonably incurred in the ordinary
course of business.

        4.5. Absence of Certain Changes or Events. Except as set forth in
Schedule 4.5, since December 31, 1998 there has not been:

             (a) Any materially adverse change in the financial position,
     results of operations, assets, liabilities, or business of Columbia Bancorp
     or the Columbia Subsidiaries, other than changes in the ordinary course of
     business;

             (b) any increase in salaries or wages of directors, officers, or
     employees of Columbia Bancorp or the Columbia Subsidiaries other than in
     the ordinary course of business; or any establishment or increase of any
     employment, compensation, bonus, pension, option, incentive or deferred
     compensation, retirement payments, profit sharing, or similar agreement or
     benefit, authorized, granted, or accrued to any directors, officers, or
     employees of Columbia Bancorp or the Columbia Subsidiaries other than in
     the ordinary course of business; or

             (c) except with respect to the three cash dividend payments
     aggregating $.24 per share paid to date and the cash dividend payment of
     $.08 per share of Common Stock declared on September 27, 1999, to be paid
     on October 29, 1999, any declaration, payment, or set aside by Columbia
     Bancorp of any dividend or distribution in respect of its Common Stock, or
     any purchase, issuance, or sale of any of its Common Stock.

        4.6. Complete and Accurate Disclosure. Neither this Plan (insofar as it
relates to Columbia Bancorp and the Columbia Subsidiaries, the Common Stock of
Columbia Bancorp, and the involvement of Columbia Bancorp in the transactions
contemplated hereby) nor any financial statement, schedule, certificate, or
other statement or document set forth on a schedule delivered by Columbia
Bancorp to Suburban Bancshares in connection with this Plan, when considered in
the aggregate, contains any statement which, at the time and in light of the
circumstances under which it is made, is false or misleading with respect to any
material fact or omits to state any material fact necessary to make the
statements contained herein or therein not false or misleading.

        4.7. Title to Properties; Absence of Liens and Encumbrances; Compliance
with Laws. Except as disclosed on Schedule 4.7, Columbia Bancorp and each of the
Columbia Subsidiaries has good and marketable title to all of their respective
properties and assets, including those reflected in the consolidated financial
statements referred to in Section 4.2, except as sold or otherwise disposed of
for fair value and only in the ordinary course of business, free and clear of
all liens and encumbrances, except (i) with respect to property as to which they

                                      A-25
<PAGE>

are lessees, (ii) with respect to real estate owned by Columbia Bancorp or the
Columbia Subsidiaries, for use, occupancy, and similar restrictions of public
record that may be observed by an inspection of the property, and such other
utility and other easements and encumbrances as do not materially adversely
affect the fair market value of such real property, and (iii) liens to secure
borrowings, liens to secure governmental deposits, and liens for current taxes
not yet due and payable. Neither Columbia Bancorp nor any of the Columbia
Subsidiaries owns or leases real property except as disclosed on Schedule 4.7,
and is not in default under any material lease of real or personal property to
which it is a party. As of the date hereof, except as disclosed on Schedule 4.7,
the real properties, structures, buildings, equipment, and the tangible personal
property owned, operated, or leased by Columbia Bancorp or any of the Columbia
Subsidiaries are (x) in good repair, order, and condition, except for depletion,
depreciation, and ordinary wear and tear, (y) suitable for the uses for which
they were intended, and (z) free from any known structural defects. As of the
date hereof, there are no laws, conditions of record, or other impediments which
materially interfere with the intended uses by Columbia Bancorp or any of the
Columbia Subsidiaries of the real property or tangible personal property owned
or leased by it, except as set forth in Schedule 4.7. Neither Columbia Bancorp
nor any of the Columbia Subsidiaries have received any notice of any violation
of any applicable law, building code, zoning ordinance, or other similar law.
Columbia Bancorp and the Columbia Subsidiaries own or have the rights to use all
real and personal properties and assets that are material to the conduct of the
business as now conducted of Columbia Bancorp and the Columbia Subsidiaries,
taken as a whole.

        4.8. Contracts. Except for the plans, contracts, and agreements of
Columbia Bancorp and the Columbia Subsidiaries (or of any plan under Section
4.8(b)) disclosed on Schedule 4.8, neither Columbia Bancorp nor any of the
Columbia Subsidiaries (nor any plan under Section 4.8(b)) is a party to or
subject to:

             (a) Any employment, consultation, or compensation contract or
     arrangement (other than those terminable at will) with any officer,
     consultant, director, or employee;

             (b) any plan, contract, program, understanding, or agreement
     providing for bonuses, pensions, severance pay, executive compensation,
     options, stock purchases, or any other form of retirement, incentive or
     deferred compensation, retirement payments, death benefits, profit sharing,
     branch closing benefits, workers' compensation, tuition reimbursement or
     scholarship program, any plans providing benefits or payments in the event
     of a change in control, change in ownership, or sale of a substantial
     portion (including all or substantially all) of the assets of Columbia
     Bancorp or any of the Columbia Subsidiaries, or any health, accident,
     disability, sick leave, vacation pay, life insurance, or other welfare
     benefit, or any other employee or retired employee benefit (including,
     without limitation, any "employee benefit plan" as defined in Section 3(3)
     of ERISA) in which any current or former employee, director, or agent (or

                                      A-26
<PAGE>

     beneficiary of any of them) of Columbia Bancorp or any of the Columbia
     Subsidiaries is or was, within the last six years, entitled to participate;

             (c) any contract or agreement with any labor union;

             (d) any lease of real or personal property with annual rentals in
     excess of $5,000;

             (e) any agreement for services in excess of $10,000 per year or for
     the purchase or disposition of any equipment or supplies except individual
     purchase orders for office supplies incurred in the ordinary course of
     business of $10,000 or less;

             (f) any instrument evidencing or relating to indebtedness for
     borrowed money except for customer accounts, deposits, certificates of
     deposit, federal funds purchased, and the like which may be construed as
     borrowings and except for loans made by Columbia Bank as lender in the
     ordinary course of its business;

             (g) any lease or other contract containing covenants not to enter
     into or consummate the transactions contemplated hereby or which provides
     for payments in excess of $2,000 and will be terminated or violated by the
     Mergers or in respect of which the Mergers would cause a default or
     acceleration of obligations; or

             (h) any other contract or agreement not of the type covered by any
     of the other specific terms of this Section 4.8 obligating Columbia Bancorp
     or any Columbia Subsidiary to expenditures in excess of $25,000.

Each of the instruments disclosed on Schedule 4.8 is valid and in full force and
effect. Neither Columbia Bancorp nor any of the Columbia Subsidiaries are in
default nor have any of them received any notice that they are in default, nor
to their actual knowledge is any other party in default, under any material
agreements, instruments, or obligations to which Columbia Bancorp or any of the
Columbia Subsidiaries is a party or by which they are bound.

        4.9. Litigation, Etc. Except as disclosed on Schedule 4.9, (a) there is
no litigation, proceeding, or investigation pending or, to the knowledge of
Columbia Bancorp, threatened against Columbia Bancorp or any of the Columbia
Subsidiaries which would result in any materially adverse change in the
condition (financial or otherwise), assets, liabilities, business, operations,
or future prospects of Columbia Bancorp and the Columbia Subsidiaries, taken as
a whole; (b) there are no outstanding orders, writs, injunctions, judgments,
decrees, directives, consent agreements, or memoranda of understanding issued by
any federal, state, or local court or governmental authority or arbitration
tribunal issued against or with the consent of Columbia Bancorp or any of the
Columbia Subsidiaries that materially and adversely affect the

                                      A-27
<PAGE>

condition (financial or otherwise), assets, liabilities, business, operations,
or future prospects or that in any manner restrict Columbia Bancorp's right to
carry on its business or that of the Columbia Subsidiaries as now conducted; and
(c) Columbia Bancorp is aware of no fact or condition now existing that might
give rise to any litigation, investigation, or proceeding which, if determined
adversely to Columbia Bancorp or any of the Columbia Subsidiaries, would
materially and adversely affect the condition (financial or otherwise), assets,
liabilities, business, operations, or future prospects of Columbia Bancorp and
the Columbia Subsidiaries, taken as a whole, or would restrict in any manner
Columbia Bancorp's right to carry on its business or that of the Columbia
Subsidiaries as now conducted. Columbia Bancorp has disclosed on Schedule 4.9
all litigation in which Columbia Bancorp or any of the Columbia Subsidiaries is
involved as a party (other than bankruptcy proceedings in which Columbia Bancorp
or any of the Columbia Subsidiaries has filed proofs of claim or routine
collection and foreclosure suits initiated in the ordinary course of business).

          4.10.  Environmental Matters. (a) Except as disclosed on Schedule 4.10
or as would not individually or in the aggregate have a materially adverse
effect on the condition (financial or otherwise), assets, liabilities, business,
or operations of Columbia Bancorp and the Columbia Subsidiaries, taken as a
whole:

                 (i)   neither Columbia Bancorp nor any of the Columbia
     Subsidiaries has received any written notices, demand letters, or written
     requests for information from any Governmental Entity or any third party
     indicating that Columbia Bancorp or any Columbia Subsidiary may be in
     violation of, or liable under, any Environmental Law;

                 (ii)  there are no civil, criminal, or administrative actions,
     suits, demands, claims, hearings, investigations, or proceedings pending or
     to the knowledge of Columbia Bancorp threatened against Columbia Bancorp or
     any Columbia Subsidiary alleging that they may be in violation of, or
     liable under, any Environmental Law;

                 (iii) no reports have been filed with any Governmental Entity,
     nor to the knowledge of Columbia Bancorp are any reports required to be
     filed with any Governmental Entity, by Columbia Bancorp or any of the
     Columbia Subsidiaries concerning the release of any Hazardous Substance or
     the violation of any Environmental Law on or at any of the Properties of
     Columbia Bancorp or any of the Columbia Subsidiaries;

                 (iv)  to the knowledge of Columbia Bancorp or except as
     disclosed on Schedule 4.10, there are no underground storage tanks on, in,
     or under any of the Properties of Columbia Bancorp or any of the Columbia
     Subsidiaries, and no underground storage tanks have been closed or removed
     from any Property of Columbia Bancorp or any of the Columbia Subsidiaries
     while such Property was owned or operated by Columbia Bancorp or any of the
     Columbia Subsidiaries;

                                      A-28
<PAGE>

                 (v)   to the knowledge of Columbia Bancorp or except as
     disclosed on Schedule 4.10, no Hazardous Substance has been generated,
     used, stored, processed, disposed of, or discharged on or into any of the
     Properties of Columbia Bancorp or any of the Columbia Subsidiaries, except
     for such hazardous substances as may be used in the everyday business of a
     bank office; and

                 (vi)  to the knowledge of Columbia Bancorp or except as
     disclosed on Schedule 4.10, no materials containing asbestos have been used
     or incorporated in any building or other structure or improvement located
     on any of the Properties of Columbia Bancorp or any of the Columbia
     Subsidiaries.

          (b)  There are no permits or licenses or agency filings or reports
required under any Environmental Law in respect of any of the Properties now or
formerly owned or operated by Columbia Bancorp or any of the Columbia
Subsidiaries that the absence of which could, individually or in the aggregate,
have a materially adverse effect on the condition (financial or otherwise),
assets, liabilities, business, or operations of Columbia Bancorp and the
Columbia Subsidiaries, taken as a whole.

          (c)  Columbia Bancorp has disclosed on Schedule 4.10 a copy of its
current policy regarding compliance with Environmental Laws.

          4.11.  Labor Matters.   To Columbia Bancorp's knowledge, no
organization effort with respect to any of the employees of Columbia Bancorp or
any of the Columbia Subsidiaries is pending or threatened, and no labor dispute,
strike, work stoppage, employee action, or labor relation problem which may
materially affect Columbia Bancorp or any of the Columbia Subsidiaries currently
is pending or threatened. Columbia Bancorp and each of the Columbia Subsidiaries
have at all times in all material respects complied with all applicable employee
termination notice and similar laws. Columbia Bancorp and each of the Columbia
Subsidiaries have at all times complied in all material respects with all
applicable family medical leave and similar laws. If applicable, Columbia
Bancorp and each of the Columbia Subsidiaries have at all times complied in all
material respects with all applicable requirements of the Worker Adjustment and
Retraining Notification Act and all similar state laws.

          4.12.  Pension and Welfare Matters.   With respect to the plans,
contracts, programs, understandings, or agreements identified pursuant to
Sections 4.8(a) and (b) (for purposes of this Section 4.12, the "plans"):

                 (a)  Schedule 4.12 clearly identifies all of the plans which
     are (i) Multiemployer Plans, (ii) Multiple Employer Plans, (iii) plans
     other than Multiemployer Plans and Multiple Employer Plans that are subject
     to Section 412 of the Code, (iv) plans intended to qualify under Section
     401 of the Code, and (v) "welfare benefit plans" within the meaning of
     Section 3(1) of ERISA which provide for continuing benefits or coverage for
     any participant or any beneficiary of a participant after such
     participant's termination of employment except

                                      A-29
<PAGE>

     coverage or benefits required by Section 4980B of the Code if paid 100% by
     the participant;

                 (b)  true, correct and complete copies of the following
     documents, with respect to each of the plans have been made available or
     delivered to Suburban Bancshares: (i) all plan documents, including trust
     agreements, insurance policies, loan documents, and service agreements and
     amendments thereto, (ii) the most recent Forms 5500 and any financial
     statements attached thereto and those for the prior three years, (iii) the
     last Internal Revenue Service determination letter and the application with
     respect thereto, (iv) summary plan descriptions, (v) the most recent
     actuarial statements and those for the prior three years, (vi) written
     descriptions of all non-written agreements relating to any such plan, as
     applicable, for Columbia Bancorp and each of the Columbia Subsidiaries, and
     (vii) all filings with a governmental agency or entity within the last
     three years, including, without limitation, filings under the voluntary or
     other compliance programs of the U.S. Department of Labor or the Internal
     Revenue Service;

                 (c)  each of the plans has been operated in all material
     respects in accordance with its terms and in accordance with all applicable
     laws including, but not limited to, the ERISA, the Code, the Consolidated
     Omnibus Budget Reconciliation Act of 1985, the Health Insurance Portability
     and Accountability Act of 1996, and state health care continuation laws;

                 (d)  all reporting and disclosure requirements of ERISA imposed
     upon each such plan have been complied with in all material respects, and
     all required governmental filings have been made with respect to the plans;

                 (e)  none of (i) the plans, (ii) the Columbia Subsidiaries, and
     (iii) Columbia Bancorp, and to Columbia Bancorp's knowledge, (x) no current
     or former director, officer, employee, agent, or representative of Columbia
     Bancorp or any of the Columbia Subsidiaries, and (y) no fiduciary, "party
     in interest" (as defined in Section 3(14) of ERISA) or "disqualified
     person" (as defined in Section 4975 of the Code) with respect to any of the
     plans has engaged in any non-exempt "prohibited transaction" in connection
     with any of the plans within the meaning of Section 4975 of the Code or
     Title I, Part 4 of ERISA;

                 (f)  none of the plans has any accumulated funding deficiency
     (as defined in Section 302 of ERISA and Section 412 of the Code), whether
     or not waived, with respect to the latest five plan years, nor any
     liability to the PBGC (other than normal premium payments);

                 (g)  with respect to plans which are pension plans (as defined
     in Section 3(2) of ERISA) subject to Title IV of ERISA, the assets of each
     such

                                      A-30
<PAGE>

     funded plans equal or exceed the liabilities (as defined in Section
     4001(a)(16) of ERISA) under such plans when such liabilities are valued on
     a termination basis using PBGC interest and other assumptions;

                 (h)  no contributions to any of the plans from Columbia Bancorp
     or any of the Columbia Subsidiaries are currently past due and, if
     applicable, all past service and other liabilities currently existing but
     payable in the future, if any, are reflected in the latest actuarial report
     in accordance with sound actuarial principles;

                 (i)  no audits, proceedings, investigations, filings, or other
     matters (excluding any determination letter application that has been or
     may be filed prior to the Effective Date) are pending before the IRS, the
     Department of Labor, the PBGC, or other public or quasi-public body in
     connection with any such plans;

                 (j)  each plan intended to qualify under Section 401(a) of the
     Code is so qualified and the trust maintained pursuant thereto is exempt
     from taxation under Section 501 of the Code and nothing has occurred with
     respect to the operation or administration of such plan which would cause
     the loss of such qualification or exemption or the imposition of any
     liability, penalty, or tax under ERISA or the Code that could reasonably be
     expected to have a material adverse effect on the condition (financial or
     otherwise), assets, liabilities, business, or operations of Columbia
     Bancorp and the Columbia Subsidiaries, taken as a whole, or on such plan;

                 (k)  except as disclosed in Schedule 4.12, through the
     Effective Date, there will be no changes in the operation of the plans or
     in the documents constituting or affecting the plans except for amendments
     and operational changes required by applicable law which do not materially
     increase the cost of such plans;

                 (l)  no employees, former employees, or retired employees of
     Columbia Bancorp or any of the Columbia Subsidiaries, as a result of their
     employment with Columbia Bancorp or any of the Columbia Subsidiaries, are
     participants in any Multiemployer Plan and neither Columbia Bancorp nor any
     of the Columbia Subsidiaries has any current, contingent, or potential
     liability with respect to any such plan;

                 (m)  no "reportable event," as such term is defined in Section
     4043(c) of ERISA, has occurred with respect to any plan since the effective
     date of ERISA, other than a reportable event for which the 30 days notice
     requirement under regulations of the PBGC has been waived;

                                      A-31
<PAGE>

                 (n)  there are no pending or threatened claims by or disputes
     with any participants or beneficiaries of the plans, except plan benefit
     claims arising in the normal course of the operations of the plans (other
     than terminated plans) and as to which no dispute exists;

                 (o)  Columbia Bancorp has no knowledge of any facts which could
     give rise to any claims against any plan or any fiduciary of any plan,
     except for plan benefit claims arising in the normal course of the
     operations of the plans (other than terminated plans);

                 (p)  neither Columbia Bancorp nor any of the Columbia
     Subsidiaries nor any fiduciary of any plan has given notice to any
     fiduciary liability insurer of any claims or potential claims in connection
     with any of the plans;

                 (q)  except as disclosed in Schedule 4.12, each of the plans
     which benefit retired employees of Columbia Bancorp or any of the Columbia
     Subsidiaries may effectively be terminated or amended, in any manner and at
     any time, without further liability to its participants, by its sponsoring
     employer;

                 (r)  neither Columbia Bancorp nor any of the Columbia
     Subsidiaries has provided, nor is required to provide, security to any
     pension plan or to any single-employer plan pursuant to Section 401(a)(29)
     of the Code or Section 307 of ERISA;

                 (s)  there has been no announcement or legally binding
     commitment by Columbia Bancorp or any of the Columbia Subsidiaries to
     create an additional plan, or to amend a plan except for amendments
     required by applicable law which do not materially increase the cost of
     such plan;

                 (t)  as to any terminated plans, all obligations for plan
     benefits or other liabilities have been satisfied in full;

                 (u)  none of the plans contains any provision which would
     prohibit the transactions contemplated by this Plan or which, except as
     disclosed in Schedule 4.12, would give rise to any severance, termination,
     or other payments or liabilities, or any forgiveness of indebtedness,
     vesting, distribution, increase in benefits, or obligations to fund
     benefits as a result of the transactions contemplated by this Plan; no
     payment that is owed or may become due any director, officer, employee, or
     agent of Columbia Bancorp or any of the Columbia Subsidiaries in connection
     with a plan will be non-deductible to the payor under Section 280G of the
     Code, and none of the Suburban Subsidiaries, Columbia Subsidiaries,
     Suburban Bancshares, and Columbia Bancorp will be required to

                                      A-32
<PAGE>

     "gross up" or otherwise compensate any person in connection with a plan
     because of the imposition of any excise tax under Section 4999 of the Code;
     and

                 (v)  no plan is funded by, associated with, or related to a
     "voluntary employees' beneficiary association" within the meaning of
     Section 501(c)(9) of the Code.

          4.13.  Related Party Transactions.  Except as disclosed on Schedule
4.13, neither Columbia Bancorp nor any of the Columbia Subsidiaries has any
contract, extension of credit, business arrangement, or other relationship of
any kind with any of the following persons:  (a) any executive officer or
director of Columbia Bancorp or any of the Columbia Subsidiaries; (b) any
stockholder owning five percent or more of the outstanding Common Stock of
Columbia Bancorp; or (c) any "affiliate" (as defined in the SEC Rule 405) of the
foregoing persons or any business in which any of the foregoing persons is an
officer, director, employee, or five percent or greater equity owner.

          4.14.  No Conflict with Other Documents.  Except as disclosed on
Schedule 4.14, neither the execution and delivery of this Plan nor the carrying
out of the transactions contemplated hereunder will result in any violation,
termination, or modification of, or be in conflict with, any terms of any
contract or other instrument to which Columbia Bancorp or any of the Columbia
Subsidiaries is a party, or of any judgment, decree, or order applicable to
Columbia Bancorp or any of the Columbia Subsidiaries, or result in the creation
of any lien, charge, or encumbrance upon any of their properties or assets,
except for any of the foregoing which would not have a material adverse effect
upon the condition (financial or otherwise), assets, liabilities, business, or
operations of Columbia Bancorp and the Columbia Subsidiaries, taken as a whole.

          4.15.  Compliance with Laws; Governmental Authorizations.  (a)  Except
where noncompliance would not have a material and adverse effect upon the
condition (financial or otherwise), assets, liabilities, business, or operations
of Columbia Bancorp and the Columbia Subsidiaries, taken as a whole, (i)
Columbia Bancorp and each of the Columbia Subsidiaries are in compliance with
all statutes, laws, ordinances, rules, regulations, judgments, orders, decrees,
directives, consent agreements, memoranda of understanding, permits,
concessions, grants franchises, licenses, and other governmental authorizations
or approvals applicable to Columbia Bancorp, the Columbia Subsidiaries, or any
of their properties; and (ii) all permits, concessions, grants, franchises,
licenses, and other governmental authorizations and approvals necessary for the
conduct of the business of Columbia Bancorp and the Columbia Subsidiaries as now
conducted have been duly obtained and are in full force and effect, and there
are no proceedings pending or, to Columbia Bancorp's knowledge, threatened which
may result in the revocation, cancellation, suspension, or materially adverse
modification of any thereof.

                 (b)  Columbia Bancorp has filed all reports that it was
required to file with the SEC under the Exchange Act, all of which complied in
all material respects with all applicable requirements of the Exchange Act and
the rules and regulations adopted thereunder. As of their

                                      A-33
<PAGE>

respective dates, each such report, statement, form, or other document,
including without limitation, any financial statements or schedules included
therein, did not contain any untrue statement of a material fact or omit to
state a material fact required to be stated therein or necessary to make the
statements therein, in light of the circumstances under which they were made,
not misleading; provided, that information as of a later date shall be deemed to
modify information as of an earlier date.

          4.16.  Authority; Enforceability.  The execution, delivery, and
performance of this Plan by Columbia Bancorp has been duly and validly
authorized by its Board of Directors, subject only to requisite approval by the
stockholders of Columbia Bancorp and appropriate governmental regulatory
authorities.  This Plan is a valid and binding agreement of Columbia Bancorp,
enforceable against it in accordance with its terms, subject as to enforcement
to bankruptcy, insolvency, fraudulent transfer, reorganization, moratorium, and
similar laws of general applicability relating to or affecting creditors' rights
and to general equity principles.

          4.17.  Insurance.  All insurance policies held by Columbia Bancorp and
the Columbia Subsidiaries relating to their operations (except for title
insurance policies), including without limitation all financial institutions
bonds, are set forth on Schedule 4.17.  All such policies are in full force and
effect.  Neither Columbia Bancorp nor any of the Columbia Subsidiaries has
received any notice of cancellation with respect to any such policies and has no
reason to expect that it will receive a notice of cancellation from any of its
present insurance carriers; provided, however, that Columbia Bancorp makes no
representation as to the effect of this Plan or the Mergers on its present
financial institutions bond or bonds.

          4.18.  Financial Institutions Bond.  Since January 1, 1993, Columbia
Bancorp and the Columbia Subsidiaries have continuously maintained in full force
and effect one or more financial institutions bonds insuring Columbia Bancorp
and the Columbia Subsidiaries against acts of dishonesty by each of their
employees.  No claim has been made under any such bond since such date, and
Columbia Bancorp is not aware of any fact or condition now existing which forms
the basis of a claim under any such bond.  Columbia Bancorp and the Columbia
Subsidiaries have no reason to expect that their present financial institutions
bond or bonds will not be renewed by their carrier on substantially the same
terms as those now in effect; provided, however, that Columbia Bancorp makes no
representation as to the effect of this Plan or the Mergers on its present
financial institutions bond or bonds.

          4.19.  Brokers; Financial Advisor.  All negotiations relating to this
Plan and the transactions contemplated hereunder have been carried on by
Columbia Bancorp directly or through its counsel or financial advisor and there
has been no intervention of any person as the result of any action of Columbia
Bancorp (and, so far as known to Columbia Bancorp, no intervention of any other
person) in such manner as to give rise to any valid claim against any of the
parties hereto for a brokerage commission, finder's fee, or other like payment
(other than to its financial advisor, Austin Financial Services, Inc.).
Schedule 4.19 is a copy of the agreement with Austin Financial Services, Inc.,
which has been engaged by Columbia Bancorp as its

                                      A-34
<PAGE>

financial advisor and to deliver an opinion as to the fairness of the
transactions contemplated by this Plan to Columbia Bancorp.

          4.20.  Beneficial Ownership of Suburban Bancshares Common Stock. As of
the date hereof, Columbia Bancorp does not beneficially own any shares of
Suburban Bancshares Common Stock or have any option, warrant, or right of any
kind to acquire the beneficial ownership of any Suburban Bancshares Common
Stock, except pursuant to the terms of this Plan, the terms of the Stock Option
Agreement attached as Appendix III, or in a fiduciary capacity.

          4.21.  Year 2000.  Columbia Bancorp has carried out a review to
evaluate the extent to which the business or operations of Columbia Bancorp or
any of the Columbia Subsidiaries will be affected by the Year 2000 Problem.  As
a result of such review, Columbia Bancorp has no reason to believe, and does not
believe, that the Year 2000 Problem will have a material adverse effect on the
condition (financial or otherwise), assets, liabilities, business, or operations
of Columbia Bancorp and the Columbia Subsidiaries, taken as a whole. Columbia
Bancorp reasonably believes that the suppliers, vendors, customers or other
material third parties used or served by Columbia Bancorp and the Columbia
Subsidiaries are addressing or will address the Year 2000 Problem in a timely
manner. Columbia Bancorp is in compliance with all applicable requirements of
any Governmental Entity relating to the Year 2000 Problem and has not received
any correspondence from or provided any written information to any Governmental
Entity relating to the Year 2000 Problem except as disclosed in Schedule 4.21.
Columbia Bancorp has provided in Schedule 4.21 copies of all of its internal
plans, including estimates of the anticipated associated costs, for addressing
the Year 2000 Problem as it relates to Columbia Bancorp and the Columbia
Subsidiaries.

  5.   Covenants of Suburban Bancshares. Except as otherwise consented to in
writing by Columbia Bancorp after the date of this Plan, Suburban Bancshares
covenants to and agrees with Columbia Bancorp as follows:

          5.1. Information.  (a) Suburban Bancshares shall, upon reasonable
notice, give to Columbia Bancorp and to its officers, accountants, counsel,
financial advisors, and other representatives, reasonable access during Suburban
Bancshares' and the Suburban Subsidiaries' normal business hours throughout the
period prior to the Effective Date to all of their properties, books, contracts,
commitments, reports of examination (consistent with applicable law), depositor
and stockholder lists, and records.  Suburban Bancshares and the Suburban
Subsidiaries will, at their own expense, furnish Columbia Bancorp during such
period with all such information concerning their affairs as Columbia Bancorp
may reasonably request, including information for use in determining if the
conditions of Section 7.1 through Section 7.10 have been satisfied, necessary to
prepare the regulatory filings or applications to be filed with governmental
regulatory authorities to obtain the approvals referred to in Section 2, and for
use in any other necessary filings to be made with appropriate governmental
regulatory authorities.

                                      A-35
<PAGE>

          (b)  Suburban Bancshares acknowledges that information received by it
concerning Columbia Bancorp and the Columbia Subsidiaries and their operations
is subject to the Confidentiality Agreement dated September 16, 1999 between
Columbia Bancorp and Suburban Bancshares (the "Confidentiality Agreement").
Without limiting the foregoing, Suburban Bancshares will not, and will cause its
representatives not to, use any information obtained pursuant to Section 6.1 for
any purpose unrelated to the consummation of the transactions contemplated by
this Plan.  Subject to the requirements of law, Suburban Bancshares will keep
confidential, and will cause its representatives to keep confidential, all
information and documents obtained pursuant to Section 6.1 unless such
information (i) was already known to Suburban Bancshares, (ii) becomes available
to Suburban Bancshares from other sources not known by Suburban Bancshares to be
bound by a confidentiality obligation, (iii) is disclosed with prior written
approval of Columbia Bancorp and the Columbia Subsidiaries, or (iv) is or
becomes readily ascertainable from published information or trade sources.  In
the event that this Plan is terminated or the transactions contemplated by this
Plan shall otherwise fail to be consummated, Suburban Bancshares shall promptly
cause all copies of documents or extracts thereof containing information and
data as to Columbia Bancorp and the Columbia Subsidiaries to be returned.  In
the event that this Plan has been terminated or the transactions contemplated
hereby shall have failed to be consummated and Suburban Bancshares or any of its
agents or representatives are requested or required (by oral questions,
interrogatories, requests for information, or documents in legal proceedings,
subpoena, civil investigative demand, or other similar process) to disclose any
of the materials delivered or obtained pursuant to the Plan (the "Columbia
Documentation"), Suburban Bancshares shall provide Columbia Bancorp with prompt
written notice of any such request or requirement so that Columbia Bancorp may
seek a protective order or other appropriate remedy.  If, in the absence of a
protective order or other remedy, Suburban Bancshares or any of its agents or
representatives are compelled to disclose any of such Columbia Documentation to
any tribunal or else stand liable for contempt or suffer other censure or
penalty, Suburban Bancshares or its agents or representatives may, without
liability hereunder, disclose to such tribunal only that portion of the Columbia
Documentation which Suburban Bancshares' counsel advises Suburban Bancshares is
legally required to be disclosed, provided, that Suburban Bancshares shall
exercise its best efforts to preserve the confidentiality of the Columbia
Documentation, including, without limitation, by cooperating with Columbia
Bancorp to obtain an appropriate protective order or other reliable assurance
that confidential treatment will be accorded the Columbia Documentation by such
tribunal.

          5.2. Events Preceding Effectiveness.  Suburban Bancshares and the
Suburban Subsidiaries will use commercially reasonable efforts to assure that
each of the events specified in Section 2 which require action on its part shall
occur on or before the Effective Date.

          5.3. Regulatory Approvals.  Suburban Bancshares and the Suburban
Subsidiaries will, where necessary, cooperate with Columbia Bancorp's efforts to
obtain all necessary regulatory approvals of the transactions contemplated by
this Plan.

          5.4. Conduct of Business.  After the date of this Plan and pending the
Effective Date, (a) Suburban Bancshares and the Suburban Subsidiaries will
conduct their business only in

                                      A-36
<PAGE>

the ordinary course; (b) Suburban Bancshares and the Suburban Subsidiaries shall
not effect any change or amendment in their respective charters or by-laws; (c)
except with respect to Suburban Bancshares stock options outstanding on the date
of this Plan which are or may become subject to exercise, Suburban Bancshares
and the Suburban Subsidiaries shall not change their authorized, issued, or
outstanding capital stock; (d) Suburban Bancshares shall not declare cash
dividends in respect of its Common Stock; (e) except as disclosed in Schedule
5.4(e), Suburban Bancshares and the Suburban Subsidiaries shall not increase
employee compensation or benefit levels (except for annual increases not in
excess of amounts established by its regular past practices), shall not
establish or make any increase in any employment, compensation, bonus, pension,
option, incentive or deferred compensation, retirement, death, profit sharing,
or similar agreements or benefits of any of its past, present, or future
officers or employees, other than additional premiums to obtain an extension of
directors' and officers' liability coverage for six years (which Suburban
Bancshares is authorized to obtain), and except as provided in this Agreement,
shall not modify the existing employment agreements with any officers or
employees; (f) Suburban Bancshares and the Suburban Subsidiaries shall not make
any change in any of their accounting policies or practices unless required by
generally accepted accounting principles or take any action which would cause
the Mergers not to be accounted for as a pooling-of-interests (and will provide
and cause Stegman & Company to provide the letters contemplated by Section
7.10); (g) Suburban Bancshares and the Suburban Subsidiaries shall not incur any
liability for borrowed money except in the ordinary course of their banking
business (i.e., may only incur variable rate loans with terms not greater than
one year) or place upon or permit any lien or encumbrance upon any of their
properties or assets except liens of the type permitted in the exceptions to
Section 3.7; and (h) notwithstanding the foregoing, upon Columbia Bancorp's
request, Suburban Bancshares shall terminate the Suburban Bancshares, Inc.
401(k) Plan, effective as of the date immediately preceding the Effective Date.
Pending the Effective Date, Suburban Bancshares and the Suburban Subsidiaries
shall (x) use commercially reasonable efforts to preserve their business
organization and assets and to keep available the services of their full-time
officers and employees, (y) continue in effect the present method of conducting
their business, and (z) consult with Columbia Bancorp as to making decisions or
actions in matters (i) other than those in the ordinary course of business, or
(ii) except as disclosed in Schedule 5.4(z)(ii), involving any capital
expenditures in excess of $25,000.

          5.5. Reservation of Shares.  Suburban Bancshares shall have reserved a
sufficient number of shares of its Common Stock for issuance upon exercise of
the option granted pursuant to the Stock Option Agreement attached as Appendix
III, which is to be executed by Columbia Bancorp and Suburban Bancshares, and
shall have taken all other actions necessary to fulfill its obligations
thereunder.

          5.6. Meeting of Stockholders of Suburban Bancshares; Document
Preparation.  (a) Suburban Bancshares will duly call and convene a meeting of
its stockholders to act upon the transactions contemplated hereby as soon as
practicable.  Except to the extent legally required for the discharge by the
board of directors of its fiduciary duties, Suburban Bancshares will recommend
approval of this Plan and the Holding Company Merger to its

                                      A-37
<PAGE>

stockholders, and will use commercially reasonable efforts to obtain a favorable
vote thereon. The calling and holding of such meeting and all notices,
transactions, documents, and information related thereto will be in material
compliance with all applicable laws.

          (b)  Suburban Bancshares shall furnish Columbia Bancorp with such
information concerning Suburban Bancshares and the Suburban Subsidiaries as is
necessary in order to cause the Proxy Statement/Prospectus (as defined in
Section 6.6), insofar as it relates to such corporations, to comply with Section
6.6.  Suburban Bancshares agrees promptly to advise Columbia Bancorp if at any
time prior to the Suburban Bancshares stockholders' meeting, any information
provided by Suburban Bancshares in the Proxy Statement/Prospectus becomes
incorrect or incomplete in any material respect and to provide Columbia Bancorp
with the information needed to correct such inaccuracy or omission.  Suburban
Bancshares shall furnish Columbia Bancorp with such supplemental information as
may be necessary in order to cause the Proxy Statement/Prospectus, insofar as it
relates to Suburban Bancshares and the Suburban Subsidiaries, to comply with
Section 6.6 after the mailing thereof to Suburban Bancshares stockholders.  The
information provided and the representations made by Suburban Bancshares to
Columbia Bancorp in connection with the Registration Statement described in
Section 6.6, both at the time such information and representations are provided
and made and at the Effective Date, will be true and accurate in all material
respects and will not contain any false or misleading statement with respect to
any material fact or omit to state any material fact required to be stated
therein or necessary in order (i) to make the statements made therein not false
or misleading, or (ii) to correct any statement contained in an earlier
communication with respect to such information or representations which has
become false or misleading.  Suburban Bancshares may rely upon all information
provided to it by Columbia Bancorp and its representatives in the preparation of
the Proxy Statement/Prospectus and shall not be liable for any untrue statement
of a material fact or any omission to state a material fact in the Proxy
Statement/Prospectus, if such statement is made in reliance upon any information
provided to it by Columbia Bancorp or by any of its officers or authorized
representatives.

          (c)  Suburban Bancshares shall promptly furnish Columbia Bancorp with
such information regarding the Suburban Bancshares stockholders as Columbia
Bancorp requires to enable it to determine what filings are required under
applicable state securities laws.  Suburban Bancshares authorizes Columbia
Bancorp to utilize in such filings the information concerning Suburban
Bancshares and the Suburban Subsidiaries provided to Columbia Bancorp in
connection with, or contained in, the Proxy Statement/Prospectus.  Suburban
Bancshares shall promptly notify Columbia Bancorp of all communications, oral,
or written, with the SEC concerning the Registration Statement and the Proxy
Statement/Prospectus.

          5.7. Consents.  Suburban Bancshares and the Suburban Subsidiaries will
use commercially reasonable efforts to obtain any consents, approvals, or
waivers from third parties required in connection with the transactions
contemplated hereunder.

          5.8. Current Information; Advice of Changes.  (a) During the period
from the date of this Plan to the Effective Date, Suburban Bancshares will cause
one or more of its

                                      A-38
<PAGE>

designated representatives to confer on a monthly or more frequent basis with
representatives of Columbia Bancorp regarding its business, operations,
properties, assets, and condition (financial or otherwise) and matters relating
to the completion of the transactions contemplated herein. As soon as reasonably
available, but in no event more than 45 days after the end of each calendar
quarter (other than the last calendar quarter of each calendar year) ending
after the date of this Plan, Suburban Bancshares will deliver to Columbia
Bancorp its quarterly reports on Form 10-Q, as filed with the SEC under the
Exchange Act. As soon as reasonably available, but in no event more than 90 days
after the calendar year, Suburban Bancshares will deliver to Columbia Bancorp
its Annual Report on Form 10-K as filed with the SEC under the Exchange Act.

          (b)  Between the date of this Plan and the Effective Date, Suburban
Bancshares shall promptly advise Columbia Bancorp in writing of any fact which,
if existing or known at the date hereof, would have been required to be set
forth or disclosed in or pursuant to this Plan or of any fact which, if existing
or known as of the date hereof, would have made any of the representations
contained herein untrue in any material respect.

          5.9. No Solicitation of Other Offers.  Suburban Bancshares agrees that
neither it nor any of the Suburban Subsidiaries nor any of their respective
officers, directors, and employees shall, and Suburban Bancshares shall direct
and use its best efforts to cause its and the Suburban Subsidiaries' agents and
representatives (including, without limitation, any investment banker, attorney,
or accountant retained by it or any of the Suburban Subsidiaries) not to,
directly or indirectly, take any action to solicit or initiate any inquiries or
the making of any offer or proposal (including without limitation any proposal
to stockholders of Suburban Bancshares) with respect to a merger, consolidation,
business combination, liquidation, reorganization, sale or other disposition of
any significant portion of assets (except problem assets shown on Schedule 5.9),
sale of shares of capital stock, or similar transactions involving Suburban
Bancshares or any of the Suburban Subsidiaries (any such inquiry, offer, or
proposal, a "Suburban Acquisition Proposal"), or, except in the opinion of
outside counsel to Suburban Bancshares as may be legally required to comply with
the duties the Board of Directors of Suburban Bancshares under applicable law
and upon receipt of a confidentially agreement with terms not materially less
favorable to Suburban Bancshares than those contained in the Confidentiality
Agreement, engage in any negotiations concerning, or provide any confidential
information or data to, or have any discussions with, any person relating to a
Suburban Acquisition Proposal.  As of the time hereof, Suburban Bancshares is
not engaged in any negotiations or discussions relating to a Suburban
Acquisition Proposal.  Suburban Bancshares shall promptly notify Columbia
Bancorp orally and in writing of, and keep it fully and currently informed on,
any Suburban Acquisition Proposal or any inquiries with respect thereto, such
written notification to include the identity of the Person making such inquiry
or Suburban Acquisition Proposal and such other information with respect thereto
as is reasonably necessary to apprise Columbia Bancorp of the material terms of
such Suburban Acquisition Proposal.  Suburban Bancshares shall give Columbia
Bancorp contemporaneous written notice upon engaging in discussions or
negotiations with, or providing any information regarding Suburban Bancshares or
any of the Suburban Subsidiaries to, any such person regarding a Suburban
Acquisition Proposal.

                                      A-39
<PAGE>

          5.10.  Affiliate Agreements.  Within 10 days of the date of this Plan,
Suburban Bancshares shall deliver or cause to be delivered to Columbia Bancorp
memoranda substantially in the form attached as Appendix V (the "Affiliates'
Memoranda") and agreements substantially in the form attached as Appendix VII
(the "Support Agreements") from each of its executive officers and directors
(and shall use commercially reasonable efforts to obtain and deliver such
memoranda and agreements from each stockholder of Suburban Bancshares who (a)
may be deemed to be an "affiliate" of Suburban Bancshares, as that term is
defined for purposes of the SEC Rules 145 and 405, or (b) may be restricted
under the accounting rules applicable to a pooling-of-interests).  Under the
terms of the Affiliates' Memoranda, each such officer, director or stockholder
shall acknowledge and agree (i) to abide by all limitations imposed by the
Securities Act and by all rules, regulations, and releases promulgated
thereunder by the SEC with respect to the sale or other disposition of the
shares of the Common Stock of Columbia Bancorp to be received by such person
pursuant to the Holding Company Merger, and (ii) to abide by all limitations
imposed by the accounting rules for the Mergers to be accounted for as a
pooling-of-interests.  Under the terms of the Support Agreements, each such
officer, director, or stockholder shall agree to support and vote the shares of
Common Stock of Suburban Bancshares owned or controlled by him or her to ratify
and confirm this Plan and the Holding Company Merger.

          5.11.  Pooling-of-Interests.  Suburban Bancshares shall use its best
efforts not to permit any of the directors, officers, employees, stockholders,
agents, consultants, or other representatives of Suburban Bancshares or any of
the Suburban Subsidiaries to take any action that would preclude Columbia
Bancorp from treating the Mergers as a pooling-of-interests for financial
reporting purposes.

          5.12.  Taxes.  Suburban Bancshares shall have filed with appropriate
federal, state, county, municipal, or foreign taxing authorities all tax returns
required to be filed (taking any applicable extensions into consideration) on or
before the Effective Date and shall have paid (or shall have made adequate
provision or set up an adequate actual reserve on the financial statements
referred to in Section 3.2 for the payment of) all taxes imposed by any taxing
authority with respect to any Pre-Closing Tax Period (as hereinafter defined),
together with any interest, additions, or penalties related to any such taxes.
For purposes of this Section 5.12, any reference to Suburban Bancshares shall be
deemed to include any corporation more than 50% of the outstanding capital stock
(by vote or value) of which is owned by Suburban Bancshares.  "Pre-Closing Tax
Period" shall mean (i) each taxable period that ends on or before the Effective
Date, and (ii) any taxable period that includes (but does not end on) the
Effective Date (the period described in this clause (ii) being hereafter
referred to as a "Straddle Period").  In the case of any tax for a Straddle
Period, the covenant in this Section 5.12 shall be limited to the Pre-Closing
Tax Amount determined as follows:

                 (a)  In the case of a periodic tax that is not based on income
     or receipts (e.g., an ad valorem property tax), the "Pre-Closing Tax
     Amount" shall be an amount equal to the amount of such tax for the entire
     Straddle Period multiplied by a fraction the numerator of which is the
     number of days elapsed

                                      A-40
<PAGE>

     between the beginning of the Straddle Period and the Effective Date, and
     the denominator of which is the total number of days in the Straddle
     Period; and

                 (b)  in the case of any other tax, the "Pre-Closing Tax Amount"
     shall be the amount of such tax for which Suburban Bancshares would have
     been liable if the Straddle Period had ended as of the close of business on
     the day of the Effective Date.

          5.13.  Public Announcements.  Between the date of this Plan and the
Effective Date, Suburban Bancshares and the Suburban Subsidiaries will consult
with Columbia Bancorp before issuing any press release or otherwise making any
public statements with respect to this Plan and the transactions contemplated
hereby and shall not issue any such press release or make any such public
statement prior to such consultation, except as counsel may advise is required
by law.

     6. Covenants of Columbia Bancorp.  Except as otherwise consented to in
writing by Suburban Bancshares after the date of this Plan, Columbia Bancorp
covenants to and agrees with Suburban Bancshares as follows:

          6.1. Information.  (a) Columbia Bancorp shall, upon reasonable notice,
give to Suburban Bancshares and to its officers, accountants, counsel, financial
advisors, and other representatives, reasonable access during Columbia Bancorp's
and the Columbia Subsidiaries' normal business hours throughout the period prior
to the Effective Date to all of their properties, books, contracts, commitments,
reports of examination (consistent with applicable law), depositor lists, and
records.  Columbia Bancorp and the Columbia Subsidiaries will, at their own
expense, furnish Suburban Bancshares during such period with all such
information concerning their affairs as Suburban Bancshares may reasonably
request, including information for use in determining if the conditions of
Section 8.1 through Section 8.09 have been satisfied and for use in any
necessary filings to be made by Suburban Bancshares or the Suburban Subsidiaries
with appropriate governmental regulatory authorities.

          (b)  Columbia Bancorp acknowledges that information received by it
concerning Suburban Bancshares and the Suburban Subsidiaries and their
operations is subject to the Confidentiality Agreement.  Without limiting the
foregoing, Columbia Bancorp will not, and will cause its representatives not to,
use any information obtained pursuant to Section 5.1 for any purpose unrelated
to the consummation of the transactions contemplated by this Plan.  Subject to
the requirements of law, Columbia Bancorp will keep confidential, and will cause
its representatives to keep confidential, all information and documents obtained
pursuant to Section 5.1 unless such information (i) was already known to
Columbia Bancorp, (ii) becomes available to Columbia Bancorp from other sources
not known by Columbia Bancorp to be bound by a confidentiality obligation, (iii)
is disclosed with prior written approval of Suburban Bancshares and the Suburban
Subsidiaries, or (iv) is or becomes readily ascertainable from published
information or trade sources.  In the event that this Plan is terminated or the
transactions contemplated by this Plan shall otherwise fail to be consummated,
Columbia Bancorp shall

                                      A-41
<PAGE>

promptly cause all copies of documents or extracts thereof containing
information and data as to Suburban Bancshares and the Suburban Subsidiaries to
be returned. In the event that this Plan has been terminated or the transactions
contemplated hereby shall have failed to be consummated and Columbia Bancorp or
any of its agents or representatives are requested or required (by oral
questions, interrogatories, requests for information, or documents in legal
proceedings, subpoena, civil investigative demand, or other similar process) to
disclose any of the materials delivered or obtained pursuant to the Plan (the
"Suburban Bancshares Documentation"), Columbia Bancorp shall provide Suburban
Bancshares with prompt written notice of any such request or requirement so that
Suburban Bancshares may seek a protective order or other appropriate remedy. If,
in the absence of a protective order or other remedy, Columbia Bancorp or any of
its agents or representatives are compelled to disclose any of such Suburban
Bancshares Documentation to any tribunal or else stand liable for contempt or
suffer other censure or penalty, Columbia Bancorp or its agents or
representatives may, without liability hereunder, disclose to such tribunal only
that portion of the Suburban Bancshares Documentation which Columbia Bancorp's
counsel advises Columbia Bancorp is legally required to be disclosed, provided,
that Columbia Bancorp shall exercise its best efforts to preserve the
confidentiality of the Suburban Bancshares Documentation, including, without
limitation, by cooperating with Suburban Bancshares to obtain an appropriate
protective order or other reliable assurance that confidential treatment will be
accorded the Suburban Bancshares Documentation by such tribunal.

          6.2. Events Preceding Effectiveness.  Columbia Bancorp and the
Columbia Subsidiaries will use commercially reasonable efforts to assure that
each of the events specified in Section 2 which require action on its part shall
occur on or before the Effective Date.

          6.3. Applications to Governmental Regulatory Authorities.  Columbia
Bancorp and the Columbia Subsidiaries will promptly prepare and file with the
appropriate governmental regulatory authorities an application requesting the
regulatory approvals referred to in Sections 2(g), 2(h), 2(i), and 2(j) and will
use commercially reasonable efforts to secure favorable action on such
applications, including without limitation commercially reasonable efforts to
pursue an appeal of a denial of a regulatory approval.

          6.4. Conduct of Business.  After the date of this Plan and pending the
Effective Date, (a) Columbia Bancorp and the Columbia Subsidiaries will conduct
their business only in the ordinary course; (b) Columbia Bancorp and the
Columbia Subsidiaries shall not effect any change or amendment in their
respective charters or by-laws; (c) except with respect to Columbia Bancorp
stock options outstanding on the date of this Plan which are or may become
subject to exercise, Columbia Bancorp and the Columbia Subsidiaries shall not
change their authorized, issued, or outstanding capital stock; (d) Columbia
Bancorp shall declare regular quarterly cash dividends in respect of its Common
Stock at the rate of not in excess of $.10 per share; (e) except as disclosed in
Schedule 6.4(e), Columbia Bancorp and the Columbia Subsidiaries shall not
increase employee compensation or benefit levels (except for annual increases
not in excess of amounts established by its regular past practices), shall not
establish or make any increase in any employment, compensation, bonus, pension,
option, incentive or deferred compensation,

                                      A-42
<PAGE>

retirement, death, profit sharing, or similar agreements or benefits of any of
its past, present, or future officers or employees, and shall not modify the
existing employment agreements with any officers or employees; (f) Columbia
Bancorp and the Columbia Subsidiaries shall not make any change in any of their
accounting policies or practices unless required by generally accepted
accounting principles or take any action which would cause the Mergers not to be
accounted for as a pooling-of-interests; and (g) Columbia Bancorp and the
Columbia Subsidiaries shall not incur any liability for borrowed money except in
the ordinary course of their banking business (i.e., may only incur variable
rate loans with terms not greater than one year) or place upon or permit any
lien or encumbrance upon any of their properties or assets except liens of the
type permitted in the exceptions to Section 4.7. Pending the Effective Date,
Columbia Bancorp and the Columbia Subsidiaries shall (x) use commercially
reasonable efforts to preserve their business organization and assets and to
keep available the services of their full-time officers and employees, (y)
continue in effect the present method of conducting their business, and (z)
consult with Suburban Bancshares as to making decisions or actions in matters
(i) other than those in the ordinary course of business, or (ii) except as
disclosed in Schedule 6.4(z)(ii), involving any capital expenditures in excess
of $25,000.

          6.5. Columbia Bancorp Common Stock.  (a) At the Effective Date, the
Columbia Bancorp Common Stock to be issued in exchange for the Suburban
Bancshares Common Stock pursuant to the terms of this Plan shall be duly
authorized, validly issued, fully paid, and non-assessable, free of preemptive
rights and free and clear of all liens, encumbrances, or restrictions created by
or through Columbia Bancorp, with no personal liability attaching to the
ownership thereof.  The Columbia Bancorp Common Stock to be issued upon exchange
for the Suburban Bancshares Common Stock pursuant to the terms of this Plan will
be issued in all material respects in accordance with applicable state and
federal laws, rules, and regulations.

          (b)  Columbia Bancorp shall have reserved a sufficient number of
shares of its Common Stock for issuance upon exercise of the option granted
pursuant to the Stock Option Agreement attached as Appendix IV, which is to be
executed by Columbia Bancorp and Suburban Bancshares, and shall have taken all
other actions necessary to fulfill its obligations thereunder.

         6.6. Registration of Shares.  Columbia Bancorp, with the assistance of
Suburban Bancshares and its representatives, will promptly file a Registration
Statement with the SEC which shall include a joint proxy statement for Columbia
Bancorp and Suburban Bancshares and a prospectus which shall satisfy all
applicable requirements of applicable state and federal laws, including the
Securities Act, the Exchange Act, and applicable state securities laws and the
rules and regulations thereunder (such joint proxy statement and prospectus,
together with any and all amendments or supplements thereto, being herein
referred to as the "Proxy Statement/Prospectus," and the various documents to be
filed by Columbia Bancorp under the Securities Act with the SEC to register the
Columbia Bancorp Common Stock into which shares of the Common Stock of Suburban
Bancshares held by stockholders will be converted, including the Proxy
Statement/Prospectus, are referred to herein as the "Registration Statement").
The number of shares to be registered will be an amount sufficient to allow all
of

                                      A-43
<PAGE>

the shares of the Common Stock of Columbia Bancorp issued to holders of the
Common Stock of Suburban Bancshares pursuant to this Plan to be registered under
the Securities Act. Columbia Bancorp will use commercially reasonable efforts to
secure the effectiveness of the Registration Statement and, after the
Registration Statement has been declared effective, will issue the shares so
registered to the holders of the Common Stock of Suburban Bancshares on the
Effective Date. Columbia Bancorp may rely upon all information provided to it by
Suburban Bancshares and its representatives in the preparation of the
Registration Statement, any post-effective amendment thereto and the Proxy
Statement and shall not be liable for any untrue statement of a material fact or
any omission to state a material fact in the Registration Statement, the post-
effective amendment, or the Proxy Statement, if such statement is made in
reliance upon any information provided to it by Suburban Bancshares or by any of
its officers or authorized representatives. Columbia Bancorp shall promptly take
all such actions as may be necessary or appropriate in order to comply in all
material respects with all applicable securities laws of any state having
jurisdiction over the transactions contemplated by this Plan and the Holding
Company Merger. Columbia Bancorp shall furnish Suburban Bancshares with copies
of all such filings and keep Suburban Bancshares advised of the status thereof.
Columbia Bancorp shall promptly notify Suburban Bancshares of all
communications, oral or written, with the SEC concerning the Registration
Statement and the Proxy Statement/Prospectus. Prior to the Effective Date,
Columbia Bancorp will cause the listing of the Common Stock of Columbia Bancorp
deliverable pursuant to this Plan on The National Market of The National
Association of Securities Dealers, Inc. ("NASDAQ").

          6.7. Meeting of Stockholders of Columbia Bancorp; Document
Preparation. (a) Columbia Bancorp shall duly call and convene a meeting of its
stockholders to act upon the transactions contemplated hereby as soon as
practicable. Except to the extent legally required for the discharge by the
board of directors of its fiduciary duties, Columbia Bancorp will recommend
approval of this Plan and the Holding Company Merger to its stockholders and
will use commercially reasonable efforts to obtain a favorable vote thereon. The
calling and holding of such meeting and all notices, transactions, documents,
and information related thereto will be in compliance with all applicable laws.

          (b)  Columbia Bancorp shall furnish such information concerning
Columbia Bancorp and the Columbia Subsidiaries as is necessary in order to cause
the Proxy Statement/Prospectus, insofar as it relates to such corporations, to
comply with Section 6.6.  Columbia Bancorp agrees promptly to advise Suburban
Bancshares if at any time prior to the Columbia Bancorp stockholders' meeting,
any information provided by Columbia Bancorp in the Proxy Statement/Prospectus
becomes incorrect or incomplete in any material respect and to provide Suburban
Bancshares with the information needed to correct such inaccuracy or omission.
Columbia Bancorp shall furnish Suburban Bancshares with such supplemental
information as may be necessary in order to cause the Proxy
Statement/Prospectus, insofar as it relates to Columbia Bancorp and the Columbia
Subsidiaries, to comply with Section 6.6 after the mailing thereof to Columbia
Bancorp stockholders.  The information provided and the representations made by
Columbia Bancorp to Suburban Bancshares in connection with the

                                      A-44
<PAGE>

Proxy Statement/Prospectus, both at the time such information and
representations are provided and made and at the Effective Date, will be true
and accurate in all material respects and will not contain any false or
misleading statement with respect to any material fact or omit to state any
material fact required to be stated therein or necessary in order (i) to make
the statements made therein not false or misleading, or (ii) to correct any
statement contained in an earlier communication with respect to such information
or representations which has become false or misleading. Columbia Bancorp may
rely upon all information provided to it by Suburban Bancshares and its
representatives in the preparation of the Proxy Statement/Prospectus and shall
not be liable for any untrue statement of a material fact or any omission to
state a material fact in the Proxy Statement/Prospectus, if such statement is
made in reliance upon any information provided to it by Suburban Bancshares or
by any of its officers or authorized representatives.

          6.8.   Consents.  Columbia Bancorp and the Columbia Subsidiaries will
use commercially reasonable efforts to obtain any consents, approvals, or
waivers from third parties required in connection with the transactions
contemplated hereunder.

          6.9.   Current Information; Advice of Changes.  (a) During the period
from the date of this Plan to the Effective Date, Columbia Bancorp will cause
one or more of its designated representatives to confer on a monthly or more
frequent basis with representatives of Suburban Bancshares regarding its
business, operations, properties, assets, and condition (financial or otherwise)
and matters relating to the completion of the transactions contemplated herein.
As soon as reasonably available, but in no event more than 45 days after the end
of each calendar quarter (other than the last calendar quarter of each calendar
year) ending after the date of this Plan, Columbia Bancorp will deliver to
Suburban Bancshares its quarterly reports on Form 10-Q, as filed with the SEC
under the Exchange Act.  As soon as reasonably available, but in no event more
than 90 days after the calendar year, Columbia Bancorp will deliver to Suburban
Bancshares its Annual Report on Form 10-K as filed with the SEC under the
Exchange Act.

          (b)  Between the date of this Plan and the Effective Date, Columbia
Bancorp shall promptly advise Suburban Bancshares in writing of any fact which,
if existing or known at the date hereof, would have been required to be set
forth or disclosed in or pursuant to this Plan or of any fact which, if existing
or known as of the date hereof, would have made any of the representations
contained herein untrue in any material respect.

          6.10.  No Solicitation of Other Offers.  Columbia Bancorp agrees that
neither it nor any of the Columbia Subsidiaries nor any of their respective
officers, directors, and employees shall, and Columbia Bancorp shall direct and
use its best efforts to cause its and the Columbia Subsidiaries' agents and
representatives (including, without limitation, any investment banker, attorney,
or accountant retained by it or any of the Columbia Subsidiaries) not to,
directly or indirectly, take any action to solicit or initiate any inquiries or
the making of any offer or proposal (including without limitation any proposal
to stockholders of Columbia Bancorp) with respect to a merger, consolidation,
business combination, liquidation, reorganization, sale or other disposition of
any significant portion of assets (except problem assets shown on Schedule

                                      A-45
<PAGE>

6.10), sale of shares of capital stock, or similar transactions involving
Columbia Bancorp or any of the Columbia Subsidiaries (any such inquiry, offer,
or proposal, a "Columbia Acquisition Proposal"), or, except in the opinion of
outside counsel to Columbia Bancorp as may be legally required to comply with
the duties the Board of Directors of Columbia Bancorp under applicable law and
upon receipt of a confidentially agreement with terms not materially less
favorable to Columbia Bancorp than those contained in the Confidentiality
Agreement, engage in any negotiations concerning, or provide any confidential
information or data to, or have any discussions with, any person relating to a
Columbia Acquisition Proposal.  As of the time hereof, Columbia Bancorp is not
engaged in any negotiations or discussions relating to a Columbia Acquisition
Proposal.  Columbia Bancorp shall promptly notify Suburban Bancshares orally and
in writing of, and keep it fully and currently informed on, any Columbia
Acquisition Proposal or any inquiries with respect thereto, such written
notification to include the identity of the Person making such inquiry or
Columbia Acquisition Proposal and such other information with respect thereto as
is reasonably necessary to apprise Suburban Bancshares of the material terms of
such Columbia Acquisition Proposal.  Columbia Bancorp shall give Suburban
Bancshares contemporaneous written notice upon engaging in discussions or
negotiations with, or providing any information regarding Columbia Bancorp or
any of the Columbia Subsidiaries to, any such person regarding a Columbia
Acquisition Proposal.

          6.11.  Affiliate Agreements.  Within 10 days of the date of this Plan,
Columbia Bancorp shall deliver or cause to be delivered to Suburban Bancshares
memoranda substantially in the form attached as Appendix VI (the "Affiliates'
Memoranda") and agreements substantially in the form attached as Appendix VIII
(the "Support Agreements") from each of its executive officers and directors
(and shall use commercially reasonable efforts to obtain and deliver such
memoranda and agreements from each stockholder of Columbia Bancorp who may be
restricted under the accounting rules applicable to a pooling-of-interests).
Under the terms of the Affiliates' Memoranda, each such officer, director or
stockholder shall acknowledge and agree to abide by all limitations imposed by
the accounting rules for the Mergers to be accounted for as a pooling-of-
interests.  Under the terms of the Support Agreements, each such officer,
director, or stockholder shall agree to support and vote the shares of Common
Stock of Columbia Bancorp owned or controlled by him or her to ratify and
confirm this Plan and the Holding Company Merger.

          6.12.  Pooling-of-Interests.  Columbia Bancorp shall use its best
efforts not to permit any of the directors, officers, employees, stockholders,
agents, consultants, or other representatives of Columbia Bancorp or any of the
Columbia Subsidiaries to take any action that would preclude Columbia Bancorp
from treating the Mergers as a pooling-of-interests for financial reporting
purposes.

          6.13.  Taxes.  Columbia Bancorp shall have filed with appropriate
federal, state, county, municipal, or foreign taxing authorities all tax returns
required to be filed (taking any applicable extensions into consideration) on or
before the Effective Date and shall have paid (or shall have made adequate
provision or set up an adequate actual reserve on the financial statements
referred to in Section 4.2 for the payment of) all taxes imposed by any taxing

                                      A-46
<PAGE>

authority with respect to any Pre-Closing Tax Period (as hereinafter defined),
together with any interest, additions, or penalties related to any such taxes.
For purposes of this Section 6.13, any reference to Columbia Bancorp shall be
deemed to include any corporation more than 50% of the outstanding capital stock
(by vote or value) of which is owned by Columbia Bancorp.  "Pre-Closing Tax
Period" shall mean each taxable period that ends on or before the Effective
Date.

          6.14. Public Announcements.  Between the date of this Plan and the
Effective Date, Columbia Bancorp and the Columbia Subsidiaries will consult with
Suburban Bancshares before issuing any press release or otherwise making any
public statements with respect to this Plan and the transactions contemplated
hereby and shall not issue any such press release or make any such public
statement prior to such consultation, except as counsel may advise is required
by law.

     7. Conditions Precedent to Columbia Bancorp's Obligations.  Unless waived
in writing by Columbia Bancorp in its sole discretion, all obligations of
Columbia Bancorp hereunder shall be subject to the fulfillment prior to or at
the Effective Date of the following conditions:

          7.1. Representations, Warranties, and Covenants.  The representations
and warranties of Suburban Bancshares herein contained shall be true in all
material respects as of the date hereof, shall be deemed made again at and as of
the Effective Date, and shall be true in all material respects as so made again;
Suburban Bancshares and the Suburban Subsidiaries shall have performed in all
material respects all obligations and agreements, and complied in all material
respects with all covenants and conditions required by this Plan to be performed
or complied with by them on or prior to the Effective Date; and Columbia Bancorp
shall have received from Suburban Bancshares an officers' certificate to their
knowledge, information, and belief in such detail as Columbia Bancorp may
reasonably request, dated the Effective Date and signed by its Chief Executive
Officer and its Secretary, to the foregoing effect.

          7.2. No Adverse Changes.  There shall not have been any materially
adverse change in the condition (financial or otherwise), results of operations,
assets, liabilities, or business of Suburban Bancshares and the Suburban
Subsidiaries, taken as a whole, from December 31, 1998 to the Effective Date.
For purposes of this Section 7.2, a "materially adverse change" shall include,
without limitation, (a) a reduction of the stockholders' equity of Suburban
Bancshares to less than $19,366,000 (plus such additions to stockholders' equity
as a result of the issuance of any Common Stock after the date of this Plan),
(b) a decrease in the net income of Suburban Bancshares for calendar year 1999
and through the Effective Date to less than $625,000, or (c) an increase in
Suburban Bancshares' ratio of non-performing assets to total assets to above
1.5%, and a "materially adverse change" shall not include expenses of the
transactions under this Plan.

          7.3. Events Preceding the Effective Date. Each of the events set forth
in Section 2 shall have occurred and any other required regulatory approvals
shall have been obtained.

                                      A-47
<PAGE>

          7.4.   Other Evidence.  Suburban Bancshares shall have delivered to
Columbia Bancorp such further certificates and documents evidencing due action
in accordance with this Plan, including certified copies of all applicable
proceedings of stockholders and directors of Suburban Bancshares and Suburban
Bank pertaining to the transactions under this Plan, as Columbia Bancorp shall
reasonably request.

          7.5.   No Adverse Proceedings, Events, or Regulatory Requirements.  No
action or proceeding against Columbia Bancorp or any of the Columbia
Subsidiaries or against Suburban Bancshares or any of the Suburban Subsidiaries
shall be pending which seeks to prevent consummation of the transactions
contemplated by this Plan; and no order of any court shall have been entered
which prohibits consummation of the Mergers and the transactions contemplated by
this Plan.  No approval, consent, waiver, or administrative action shall have
included any condition or requirement that would (i) result in a materially
adverse effect on Columbia Bancorp or Suburban Bancshares, or (ii) so materially
and adversely affect the economic or business benefits of the Mergers that
Columbia Bancorp, in the sole judgment of Columbia Bancorp, would not have
entered into this Plan had such conditions or requirements been known at the
date hereof.

          7.6.   Consents, Etc.  All requisite consents, approvals, waivers,
undertakings, memoranda, agreements, exercises, and terminations by third
parties which Suburban Bancshares and the Suburban Subsidiaries have covenanted
to use commercially reasonable efforts to obtain under Sections 5.7, 5.10, and
5.11 shall have been obtained by Suburban Bancshares or waived by Columbia
Bancorp.

          7.7.   Opinion of Tax Counsel.  Columbia Bancorp shall have received a
opinion from its tax counsel, dated the Effective Date, in form and substance
reasonably satisfactory to Columbia Bancorp, covering the matters set forth in
Appendix IX.  In rendering such opinion, tax counsel shall require delivery of
and rely upon certain representation letters delivered by Columbia Bancorp,
Suburban Bancshares, and certain stockholders of Suburban Bancshares, which
letters shall be in form and substance satisfactory to tax counsel.

          7.8.   Fairness Opinion.  Columbia Bancorp shall have received a
written opinion from Austin Financial Services, Inc. (or such other recognized
investment firm as Columbia Bancorp may select), dated contemporaneously with
the date of the Proxy Statement, to the effect that the consideration to be
received in the Holding Company Merger is fair to the stockholders of Columbia
Bancorp from a financial point of view.

          7.9.   Opinion of Counsel.  Columbia Bancorp shall have received an
opinion of counsel to Suburban Bancshares, dated the Effective Date, in form and
substance reasonably satisfactory to Columbia Bancorp, covering the matters set
forth in Appendix X.

          7.10.  Pooling-of-Interests Accounting.  Columbia Bancorp shall have
received a letter from KPMG LLP to the effect that the Mergers qualify for
pooling-of-interests accounting treatment if consummated in accordance with this
Plan; provided, that such condition shall be

                                      A-48
<PAGE>

void and of no further force and effect if Columbia Bancorp has not received
such letter because of any action or inaction of Columbia Bancorp. In rendering
such letter, KPMG LLP shall require delivery of and rely upon certain
representation letters delivered by Columbia Bancorp and Suburban Bancshares and
a pooling letter delivered by Stegman & Company, which letters shall be in form
and substance satisfactory to KPMG LLP.

     8.    Conditions Precedent to Suburban Bancshares' Obligations. Unless
waived in writing by Suburban Bancshares in its sole discretion, all obligations
of Suburban Bancshares hereunder shall be subject to the fulfillment prior to or
at the Effective Date of the following conditions:

               8.1. Representations, Warranties, and Covenants. The
representations and warranties of Columbia Bancorp herein contained shall be
true in all material respects as of the date hereof, shall be deemed made again
at and as of the Effective Date, and shall be true in all material respects as
so made again; Columbia Bancorp and the Columbia Subsidiaries shall have
performed in all material respects all obligations and agreements, and complied
in all material respects with all covenants and conditions required by this Plan
to be performed or complied with by them on or prior to the Effective Date; and
Suburban Bancshares shall have received from Columbia Bancorp an officers'
certificate to their knowledge, information and belief in such detail as
Suburban Bancshares may reasonably request, dated the Effective Date and signed
by its Chief Executive Officer and its Secretary, to the foregoing effect.

               8.2. No Adverse Changes. There shall not have been any materially
adverse change in the condition (financial or otherwise), results of operations,
assets, liabilities, or business of Columbia Bancorp and the Columbia
Subsidiaries, taken as a whole, from December 31, 1998 to the Effective Date.
For purposes of this Section 8.2, a "materially adverse change" shall include,
without limitation, (a) a reduction of the stockholders' equity of Columbia
Bancorp to less than $38,000,000 (plus such additions to stockholders' equity as
a result of the issuance of any Common Stock after the date of this Plan), (b) a
decrease in the net income of Columbia Bancorp for calendar year 1999 and
through the Effective Date to less than $3,400,000, or (c) an increase in
Columbia Bancorp's ratio of non-performing assets to total assets to above 1.5%,
and a "materially adverse change" shall not include expenses of the transactions
under this Plan.

               8.3. Events Preceding the Effective Date.  Each of the events set
forth in Section 2 shall have occurred and any other required regulatory
approvals shall have been obtained.

               8.4. Other Evidence.  Columbia Bancorp shall have delivered to
Suburban Bancshares such further certificates and documents evidencing due
action in accordance with this Plan, including certified copies of all
applicable proceedings of stockholders and directors of Columbia Bancorp and
Columbia Bank pertaining to the transactions under this Plan, as Suburban
Bancshares shall reasonably request.

                                      A-49
<PAGE>

               8.5. No Adverse Proceedings, Events, or Regulatory Requirements.
No action or proceeding against Columbia Bancorp or any of the Columbia
Subsidiaries or against Suburban Bancshares or any of the Suburban Subsidiaries
shall be pending which seeks to prevent consummation of the transactions
contemplated by this Plan; and no order of any court shall have been entered
which prohibits consummation of the Mergers and the transactions contemplated by
this Plan. No approval, consent, waiver, or administrative action shall have
included any condition or requirement that would (i) result in a materially
adverse effect on Columbia Bancorp or Suburban Bancshares, or (ii) so materially
and adversely affect the economic or business benefits of the Mergers that
Suburban Bancshares, in the sole judgment of Suburban Bancshares, would not have
entered into this Plan had such conditions or requirements been known at the
date hereof.

               8.6. Consents, Etc.  All requisite consents, approvals, or
waivers, undertakings, memoranda, agreements, exercises, and terminations by
third parties which Columbia Bancorp has covenanted to use commercially
reasonable efforts to obtain under Sections 6.8, 6.11, and 6.12 shall have been
obtained by Columbia Bancorp or waived by Suburban Bancshares.

               8.7. Opinion of Tax Counsel. Suburban Bancshares shall have
received an opinion from tax counsel to Columbia Bancorp, dated the Effective
Date, in form and substance reasonably satisfactory to Suburban Bancshares,
covering the matters set forth in Appendix IX. In rendering such opinion, tax
counsel shall require delivery of and rely upon certain representation letters
delivered by Columbia Bancorp, Suburban Bancshares, and certain stockholders of
Suburban Bancshares, which letters shall be in form and substance satisfactory
to tax counsel.

               8.8. Fairness Opinion. Suburban Bancshares shall have received a
written opinion from Danielson Associates Inc. (or such other recognized
investment firm as Suburban Bancshares may select), dated contemporaneously with
the date of the Proxy Statement, to the effect that the consideration to be
received in the Holding Company Merger is fair to the stockholders of Suburban
Bancshares from a financial point of view.

               8.9. Opinion of Counsel. Suburban Bancshares shall have received
an opinion of counsel to Columbia Bancorp, dated the Effective Date, in form and
substance reasonably satisfactory to Suburban Bancshares, covering the matters
set forth in Appendix XI.

     9.    Terms of the Holding Company Merger.

               9.1. Structure of the Holding Company Merger. At the Effective
Date, subject to the terms and conditions of this Plan, Suburban Bancshares will
merge with and into Columbia Bancorp, the separate corporate existence of
Suburban Bancshares shall cease, and Columbia Bancorp shall continue as the
successor corporation (the "Successor Corporation"). From and after the
Effective Date, the Holding Company Merger shall have the effects set forth in
Md. General Corporation law (S) 3-114 and De. General Corporation law (S)(S)
259 - 261.

                                      A-50
<PAGE>

               9.2. Conversion of Stock; Conversion Ratio.  (a) On the Effective
Date, each share of the Suburban Bancshares Common Stock outstanding immediately
prior to the Effective Date (other than shares (the "Dissenters' Shares'') with
respect to which dissenter's rights shall have been perfected in accordance with
De. General Corporation Law ss 262), shall, without any action on the part of
the holder thereof, be canceled and converted into the number of shares of
Successor Corporation Common Stock (rounded to the nearest 0.01 share) which
results after multiplication by the Conversion Ratio. The Conversion Ratio shall
be 0.2196; provided, however, that the Conversion Ratio shall be increased (but
not decreased) to the extent necessary to cause the average market value (based
on the mean of the daily high and low trade prices, or, if none, of the daily
high bid and low asked prices, reported on NASDAQ) of Columbia Bancorp Common
Stock (for each of the 10 trading days ending on the trading date that is three
days before the Effective Date) received for each share of Suburban Bancshares
Common Stock to be $3.00 per share; provided, further that such adjustment may
not increase the Conversion Ratio above 0.2338.

               (b)  No certificates for fractional shares of Successor
Corporation Common Stock shall be issued; in lieu thereof, each holder otherwise
entitled to a fractional interest shall receive an amount in cash based on the
market value of Columbia Bancorp Common Stock as determined in Section 9.2. Each
such holder shall have no other rights with respect to such fractional interest.

               (c)  Dissenters' Shares shall be paid for in accordance with De.
General Corporation Law ss 262 and thereupon shall be cancelled, retired and
cease to exist.

               (d)  Notwithstanding any provision of this Plan to the contrary,
any Dissenters' Shares, which as of the Effective Date the holder thereof has
not withdrawn or lost any right to such appraisal shall not be exchanged, or
represent a right to receive shares of Columbia Bancorp Common Stock, but the
holder shall only be entitled to such rights as are granted by De. General
Corporation Law ss 262. If a stockholder of Suburban Bancshares who demands
appraisal of his shares under De. General Corporation Law ss 262 shall
effectively withdraw or lose (through failure to perfect or otherwise) the right
to appraisal, then, as of the Effective Date or the occurrence of such event,
whichever last occurs, that stockholder's shares of the Suburban Bancshares
Common Stock shall be exchanged and represent only the right to receive shares
of Columbia Bancorp Common Stock as provided in Section 9.2(a) pursuant to the
procedures in Section 9.3. Suburban Bancshares shall give Columbia Bancorp (a)
prompt written notice of any written demands for appraisal of any share of the
Suburban Bancshares Common Stock, attempted withdrawals of such demands and any
other instruments served pursuant to the De. General Corporation Law ss 262
relating to the Suburban Bancshares stockholders' rights of appraisal and (b)
the opportunity to direct all negotiations and proceedings with respect to
demands for appraisal under De. General Corporation Law ss 262. Suburban
Bancshares shall not, except with the prior written consent of Columbia Bancorp,
voluntarily make any payment with respect to any demands for appraisals of share
of the Suburban Bancshares Common Stock, offer to settle or settle any such
demands or approve any withdrawal of any such demands. Notwithstanding any
provision of this Plan to the contrary, Columbia Bancorp shall have the right to
terminate this Plan and be released from all obligations hereunder if,
immediately prior to the proposed Effective Date, Suburban Bancshares
stockholders holding in excess of ___% of the outstanding shares of the Suburban
Bancshares Common Stock have demanded appraisal rights (which demands
theretofore have not been withdrawn) so as to jeopardize the accounting
treatment specified in Section 7.10 and, KPMG LLP fails or refuses to deliver a
letter to Columbia Bancorp to the effect that the Mergers qualify for
pooling-of-interests accounting treatment, as provided in Section 7.10.

               9.3. Exchange Procedure.  (a) After the Effective Date,
certificates representing such shares of Common Stock of Suburban Bancshares
shall represent the right to receive certificates representing shares of Common
Stock of Successor Corporation determined in accordance with Section 9.2; such
Suburban Bancshares certificates at any time after the Effective Date may be
exchanged by the holders thereof for new certificates for the appropriate number
of shares of Common Stock of Successor Corporation by forwarding such Suburban
Bancshares Common Stock certificates and the letter of transmittal provided by
Successor Corporation to the transfer agent for Successor Corporation Common
Stock, and the payment of cash in lieu of fractions, dividends, and other
distributions on said stock may be withheld until the Suburban Bancshares
certificates are surrendered for exchange to the transfer agent for Successor
Corporation Common Stock; when such new certificates are issued, the holders
thereof shall be entitled to be paid the amount (without any interest thereon)
of all such withheld cash in lieu of fractions, dividends, or other
distributions which have theretofore become payable with respect to such shares
of Common Stock of Successor Corporation.

               (b)  As soon as possible after the Effective Date, the transfer
agent for Successor Corporation Common Stock shall send or cause to be sent a
notice and transmittal form to each record holder of a certificate theretofore
evidencing shares of the Suburban Bancshares Common Stock.

               (c)  All shares of Successor Corporation Common Stock into which
shares of Suburban Bancshares Common Stock shall have been converted shall be
deemed to have been issued in full satisfaction of all rights pertaining to such
shares of Suburban Bancshares Common Stock.

                                      A-51
<PAGE>

               9.4. Stock Options.  (a)  At the Effective Date, all options
granted by Suburban Bancshares which are outstanding under all Stock Option
Plans previously adopted by Suburban Bancshares to purchase shares of Suburban
Bancshares Common Stock, which are outstanding and unexercised immediately prior
thereto (each, an "Outstanding Option"), shall be converted as to each whole
share subject to such Outstanding Option into an option (each, an "Exchange
Option") to purchase a number of shares of Successor Corporation Common Stock
equal to the number of shares of Suburban Bancshares Common Stock which could
have been purchased under the Outstanding Option multiplied by the Conversion
Ratio, with the total for each holder's Exchange Options with the same option
price and expiration date rounded down to the next whole share.

               (b)  The per share exercise price of each Exchange Option shall
be equal to the price per share set forth in the Outstanding Option divided by
the Conversion Ratio, rounded up to the nearest whole cent.

               (c)  The Exchange Option shall otherwise have the same duration
and other terms as the Outstanding Option.

               (d)  The adjustments provided herein with respect to any options
which are "incentive stock options" (as defined in Section 422 of the Code)
shall be effected in a manner consistent with Section 424(a) of the Code.

               9.5. Charter of the Successor Corporation. The Charter of
Columbia Bancorp, as in effect immediately prior to the Effective Date, shall be
the Charter of the Successor Corporation until thereafter amended as provided by
law.

               9.6. By-Laws of the Successor Corporation. The By-Laws of
Columbia Bancorp, as in effect immediately prior to the Effective Date (with the
amendments set forth in Appendix XII), shall be the By-Laws of the Successor
Corporation until thereafter amended as provided by law.

               9.7. Anti-Dilution Provision. If Columbia Bancorp takes any
action which establishes, prior to the Effective Date, a record date or
effective date for a stock dividend on its Common Stock, a split or reverse
split of its Common Stock or any distribution on all shares of its Common Stock
other than cash dividends, Columbia Bancorp will take such action as shall be
necessary in order that each share of Common Stock of Suburban Bancshares will
be converted into the same number of shares of the Common Stock of Successor
Corporation (whether such number is greater or less than the number otherwise
provided for herein) that the owner of such shares would have owned immediately
after the record date or effective date of such event had the Effective Date
occurred immediately before such record date or effective date, and the
Conversion Ratio set forth in Section 9.2 shall be adjusted accordingly.
Suburban Bancshares hereby agrees to any revision in the exchange ratio pursuant
to this Section 9.7.

                                      A-52
<PAGE>

               9.8. Restriction on Issuance or Repurchase of Securities.  Except
transactions that would preclude the issuance of the pooling-of-interest letter
under Section 7.10, nothing in this Plan shall limit the right of Columbia
Bancorp to amend its Charter and By-Laws and to issue or repurchase any of its
stock or other securities in any manner and for any consideration permitted by
law either in connection with acquisitions of new affiliates or otherwise, prior
to or after the Effective Date.

     10.   Terms of the Bank Merger.

               10.1. Structure of the Bank Merger. At the Effective Date,
subject to the terms and conditions of this Plan, Suburban Bank will merge with
and into Columbia Bank, the separate corporate existence of Suburban Bank shall
cease, and Columbia Bank shall continue as the successor banking institution
(the "Successor Bank"). From and after the Effective Date, the Bank Merger shall
have the effects set forth in Md. Fin. Ins. Code (S) 3-712.

               10.2.  Conversion of Stock; Conversion Ratio. On the Effective
Date, each share of the Suburban Bank Common Stock outstanding immediately prior
to the Effective Date, shall, without any action on the part of the holder
thereof, be canceled.

               10.3.  Exchange Procedure.  (a) After the Effective Date,
certificates representing such shares of Common Stock of Suburban Bank shall
represent the right to receive certificates representing shares of Common Stock
of Successor Bank determined in accordance with Section 10.2; such Suburban Bank
certificates at any time after the Effective Date may be exchanged by Columbia
Bancorp for new certificates for the appropriate number of shares of Common
Stock of Successor Bank.

               (b)  All shares of Successor Bank Common Stock into which shares
of Suburban Bank Common Stock shall have been converted shall be deemed to have
been issued in full satisfaction of all rights pertaining to such shares of
Suburban Bank Common Stock.

               10.4.  Charter of the Successor Bank. The Charter of Columbia
Bank, as in effect immediately prior to the Effective Date, shall be the Charter
of the Successor Bank until thereafter amended as provided by law.

               10.5.  By-Laws of the Successor Bank. The By-Laws of Columbia
Bank, as in effect immediately prior to the Effective Date (with the amendments
set forth in Appendix XIII), shall be the By-Laws of the Successor Bank until
thereafter amended as provided by law.

               10.6.  Restriction on Issuance or Repurchase of Securities.
Nothing in this Plan shall limit the right of Columbia Bank to amend its Charter
and By-Laws and to issue or repurchase any of its stock or other securities in
any manner and for any consideration permitted by law either in connection with
acquisitions of new affiliates or otherwise, prior to or after the Effective
Date.

                                      A-53
<PAGE>

     11.    Boards of Directors and Employment Matters. Upon the Effective Date
or as otherwise indicated:

               (a)  At Effective Date, the Board of Directors of Successor
     Corporation will be increased by five members. All of the directors of
     Columbia Bancorp immediately prior to the Effective Date shall continue as
     directors of Successor Corporation after the Effective Date, and five of
     the directors of Suburban Bancshares before the Effective Date will become
     directors of Successor Corporation as shown on Appendix XIV.

               (b)  At Effective Date, the Board of Directors of Successor Bank
     will be increased by five members. All of the directors of Columbia Bank
     immediately prior to the Effective Date shall continue as directors of
     Successor Bank after the Effective Date, and five of the directors of
     Suburban Bank before the Effective Date will become directors of Successor
     Bank as shown on Appendix XIII.

               (c)  The members the Boards of Directors having board titles and
     the persons serving as executive officers of Successor Corporation and
     Successor Bank at the Effective Date are listed on Appendix XIV. The
     employment of all officers and employees of Suburban Bancshares, other than
     the officer with an employment agreement from Successor Corporation and
     listed on Appendix XIV (the "Bancorp Contract Employee"), will terminate
     without compensation or benefits of any kind or form immediately prior to
     the Effective Date, and none will become officers or employees of Successor
     Corporation except as listed on Appendix XIV. The chief executive
     officer/board chairman's service agreement of the Bancorp Contract Employee
     will terminate immediately prior to the Effective Date without payment or
     benefits of any kind or form, and the Bancorp Contract Employee will be
     offered an employment agreement with Successor Corporation in the form
     attached as Appendix IX.

               (d)  The officers and employees of Suburban Bank, other than the
     officers and employees with an employment agreement from Successor Bank and
     listed on Appendix XIV (the "Bank Contract Employees"), will continue as
     officers and employees of Successor Bank as at-will employees. The
     severance agreements of officers listed on Appendix XIV will be assumed by
     Successor Bank, and the other officers or employees of Suburban Bank (other
     than the Bank Contract Employees) becoming officers or employees of
     Successor Bank upon termination of employment by Successor Bank within four
     months of the Effective Date will receive a severance payment equal to one
     week's pay (rounded to the nearest one-tenth of a week) for each year's
     service with Suburban Bank (with a minimum payment of four weeks' pay and a
     maximum payment of 12 weeks' pay). The chief executive officer/board
     chairman's service agreement and the employment agreement of the Bank
     Contract Employees (whether with

                                      A-54
<PAGE>

     Suburban Bancshares or Suburban Bank) will terminate immediately prior to
     the Effective Date without payment or benefits of any kind or form, and the
     Bank Contract Employees will be offered employment agreements with the
     Successor Bank in the forms attached as Appendix XV and Appendix XVI.

               (e)  Successor Corporation will provide the employees of Suburban
     Bank who continue as at-will employees of Successor Bank after the
     Effective Date with benefits under Successor Corporation's employee benefit
     plans to the extent they are eligible to do so under the terms of such
     plans or programs as are in force on the Effective Date, with credit given
     for their prior service with Suburban Bank for purposes of allocation,
     eligibility, and vesting. In that connection, Successor Corporation may, in
     its sole discretion, freeze or terminate the employee benefit plans of
     Suburban Bancshares, merge them with one or more employee benefit plans of
     Successor Corporation, or continue to maintain them.

     12.    Amendment of this Plan. This Plan may be amended at any time prior
to the Effective Date in response to comments of governmental regulatory
authorities, or otherwise; provided, that any such amendment is in writing and
is approved by the Board of Directors of each of the parties hereto.

     13.    Abandonment of this Plan; Effect Thereof. Anything herein to the
contrary notwithstanding, and notwithstanding any stockholder vote or approval,
this Plan may be terminated and abandoned:

               (a)  by mutual consent of the Boards of Directors of Suburban
     Bancshares and Columbia Bancorp;

               (b)  by Columbia Bancorp or Suburban Bancshares, if its Board of
     Directors so determines, in the event of the failure of the stockholders of
     Columbia Bancorp or the stockholders of Suburban Bancshares to approve this
     Plan at the meetings called to consider such approval, unless in each case
     the failure of such occurrence shall be due to the failure of the party
     seeking to terminate this Plan to perform or observe its agreement set
     forth herein to be performed or observed by such party at or before the
     Effective Date;

               (c)  by Columbia Bancorp or Suburban Bancshares, if its Board of
     Directors so determines, in the event of a material breach by the other
     party hereto of any representation, warranty, covenant, or agreement
     contained herein which is not cured or not curable within 60 days after
     written notice of such breach is given to the party committing such breach
     by the other party;

               (d)  by Columbia Bancorp by written notice to Suburban Bancshares
     if prior to June 30, 2000 (i) any approval, consent, or waiver of any

                                      A-55
<PAGE>

     Governmental Entity required to permit consummation of the transactions
     contemplated hereby shall have been denied, (ii) any approval, consent, or
     waiver of any Governmental Entity required to permit consummation of the
     transactions contemplated hereby shall include any condition or requirement
     that would (i) result in a materially adverse effect on Columbia Bancorp or
     Suburban Bancshares, or (ii) so materially and adversely affect the
     economic or business benefits of the Mergers that Columbia Bancorp, in the
     sole judgment of Columbia Bancorp, would not have entered into this Plan
     had such conditions or requirements been known at the date hereof, (iii)
     any action or proceeding against Columbia Bancorp or any of the Columbia
     Subsidiaries or against Suburban Bancshares or any of the Suburban
     Subsidiaries shall be pending which seeks to prevent consummation of the
     transactions contemplated by this Plan, (iv) any court shall have entered
     an order which prohibits consummation of the Mergers and the transactions
     contemplated by this Plan or (v) termination is permitted as provided in
     Section 9.2(d);

               (e)  by Columbia Bancorp or Suburban Bancshares, by action of the
     Board of Directors of either party and the delivery of written notice by
     either party to the other, in the event that the Mergers are not
     consummated by June 30, 2000, unless the failure to so consummate by such
     time is due to the breach of any representation, warranty, agreement, or
     covenant contained in this Plan by the party seeking to terminate, or if
     prior to June 30, 2000, any Governmental Entity of competent jurisdiction
     shall have issued a final, unappealable order or ruling enjoining or
     otherwise prohibiting consummation of the transactions contemplated by this
     Plan;

               (f)  by action of the Board of Directors of Suburban Bancshares
     in their sole discretion if they determine to negotiate a Suburban
     Acquisition Proposal under Section 5.9;

               (g)  by action of the Board of Directors of Columbia Bancorp in
     their sole discretion if they determine to negotiate a Columbia Acquisition
     Proposal under Section 6.10; or

               (h)  by Columbia Bancorp or Suburban Bancshares, by action of the
     Board of Directors of either party in their sole discretion and the
     delivery of written notice by either party to the other within 10 business
     days of the date hereof, in the event that Columbia Bancorp or Suburban
     Bancshares, as the case may be, is not satisfied with the results of its
     review of the loan and related files and reports of the other (as to which
     full access will be given under Sections 5.1 and 6.1).

Except as provided in Section 17, in the event of the termination of this Plan
by either Columbia Bancorp or Suburban Bancshares, as provided above, this Plan
shall thereafter become void, and there shall be no liability on the part of any
party hereto or their respective officers or directors,

                                      A-56
<PAGE>

except that any such termination shall be without prejudice to the rights of any
party hereto arising out of the willful breach of any other party of any
covenant or willful misrepresentation contained in this Plan.

     14.    Expenses.  Whether or not the transactions hereunder are
consummated, each party to the Plan shall pay its own expenses relating hereto,
including fees and disbursements of its counsel and accountants and one half of
filing fees in respect of bank regulatory approvals required in order to
consummate the Mergers; provided, however, that Columbia Bancorp shall pay (a)
the registration fee of the SEC, filing fees in respect of state "blue sky"
laws, and the fee payable to The National Association of Securities Dealers,
Inc. in respect of the listing on NASDAQ of the shares of Columbia Bancorp
Common Stock to be issued pursuant to this Plan, and (b) the costs of printing
and mailing the Proxy Statement/Prospectus. The foregoing shall not be construed
as a limitation of damages in the event of breach.

     15.    Notices.  All notices, requests, demands, and other communications
under or connected with this Plan shall be in writing, and (a) if to Columbia
Bancorp, shall be addressed to Columbia Bancorp, 9171 Baltimore National Pike,
Ellicott City, Maryland 21042, attention of John M. Bond, Jr., President and
Chief Executive Officer, with a copy to its counsel, Piper & Marbury l.l.p., 36
South Charles Street, Baltimore, Maryland 21201-3010, attention of James J.
Winn, Jr., Esquire; or (b) if to Suburban Bancshares, shall be addressed to
Suburban Bancshares, Inc., 7505 Greenway Center Drive, Greenbelt, Maryland
20768, attention of Winfield M. Kelly, Jr., Chairman of the Board and Chief
Executive Officer, with a copy to its counsel, McNamee, Hosea, Jernigan & Kim,
P.A., 6411 Ivy Lane, Suite 200, Greenbelt, Maryland 20770, attention of Stephen
C. Hosea, Esquire.  Any such notices, requests, demands, and other
communications shall be mailed, postage prepaid, first class mail, or delivered
personally and shall be sufficient and effective when delivered to or received
at the address as specified.  Each of the parties may change the address at
which it is to receive communications by like written notice to the other.

     16.    Entire Agreement; Effect. Subject to Sections 5.1(b) and 6.1(b),
this Plan (including the financial statements, lists, schedules, and documents
delivered pursuant hereto, which are made a part hereof) is intended by the
parties to and does constitute the entire agreement of the parties with respect
to the transaction contemplated hereunder. This Plan supersedes any and all
prior understandings, including prior letters of intent, and it may not be
changed, waived, discharged, or terminated orally, but only in writing by a
party against which enforcement of the change, waiver, discharge, or termination
is sought.

     17.    Representations, Warranties, and Agreements.  Except as set forth in
this Section 17, all representations, warranties, and agreements of Columbia
Bancorp and Suburban Bancshares made in this Plan, or in any instrument
delivered by Columbia Bancorp or Suburban Bancshares pursuant to this Plan,
shall expire at the Effective Date.  In the event of the consummation of the
transactions contemplated hereby, the agreements contained in or referred to in
Sections 9, 10, and 11 shall survive the Effective Date.  In the event of the
termination of this Plan in accordance with its terms, the agreements contained
in or referred to in Sections 5.1(b), 5.5, 5.9, 6.1(b), 6.5(b), 6.10, and 14,
the Stock Option Agreements, and the Support

                                      A-57
<PAGE>

Agreements (which shall only terminate in accordance with their respective
terms) shall survive such termination. Except to the extent that
representations, warranties, and agreements of Columbia Bancorp and Suburban
Bancshares made in this Plan, or in any instrument delivered by Columbia Bancorp
or Suburban Bancshares pursuant to this Plan, shall expire at the Effective
Date, nothing contained herein shall be construed to limit the liability of a
party to another party for damages caused by a breach of this Plan.

     18.    Governing Law. This Plan shall be governed by, and shall be
interpreted in accordance with, the laws of the State of Maryland or, to the
extent applicable, the federal laws of the United States of America or the laws
of the State of Delaware.

     19.    General. The section headings contained in this Plan are for
reference purposes only and shall not affect in any way the meaning or
interpretations of this Plan. This Plan may be executed simultaneously in two or
more counterparts, each of which shall be deemed an original, but all of which
together shall constitute one and the same instrument. This Plan shall inure to
the benefit of and be binding upon the parties hereto and their respective
successors but shall not be assigned to and shall not create any rights in favor
of any other party. Any purported assignment in violation of this Section 19
shall be void.

     IN WITNESS WHEREOF, Columbia Bancorp and Suburban Bancshares have caused
this Plan to be duly executed by their respective chairmen or presidents, and
their respective seals to be hereunto affixed and attested by their respective
secretaries, thereunto duly authorized as of the date first above written.

ATTEST:      [SEAL]                 COLUMBIA BANCORP


___________________________         By:______________________________________
John A. Scaldara, Jr.                  John M. Bond, Jr.
Secretary                              President and Chief Executive Officer

ATTEST:      [SEAL]                 SUBURBAN BANCSHARES, INC.


___________________________         By:______________________________________
                                       Winfield M. Kelly, Jr.
Secretary                              Chairman of the Board
                                       and Chief Executive Officer

                                      A-58
<PAGE>

                                  APPENDIX B

                     SUPPORT AGREEMENT OF COLUMBIA BANCORP

                                      B-1
<PAGE>

                           FORM OF SUPPORT AGREEMENT

     THIS SUPPORT AGREEMENT (this "Agreement") dated as of September 28, 1999,
between SUBURBAN BANCSHARES INC., a Delaware corporation and registered bank
holding company ("Suburban Bancshares"), and each of the individuals listed on
Schedule A attached hereto (collectively, the "Columbia Bancorp Stockholders").

                              W I T N E S S E T H:

     WHEREAS, the Columbia Bancorp Stockholders (i) collectively possess the
sole or joint right to vote, or direct the voting of, an aggregate of
___________ shares of common stock, par value $.01 per share (the "Shares"), of
Columbia Bancorp, a Maryland corporation and registered bank holding company
("Columbia Bancorp"), which constitute approximately _____ % of the outstanding
capital stock of Columbia Bancorp, and (ii) individually possess the right to
vote, or to direct the voting of, the number of Shares set forth opposite such
Columbia Bancorp Stockholder's name on Schedule A hereto; and

     WHEREAS, the Columbia Bancorp Stockholders (i) collectively possess the
sole or joint power to dispose of, or to direct the disposition of, an aggregate
of ___________ Shares, which constitute approximately _____ % of the outstanding
capital stock of Columbia Bancorp, and (ii) individually possess the power to
dispose of, or direct the disposition of, the number of Shares set forth
opposite such Columbia Bancorp Stockholder's name on Schedule A hereto; and

     WHEREAS, Columbia Bancorp has entered into a Plan and Agreement to Merge
with Suburban Bancshares, dated as of the business day immediately prior to the
date hereof (the "Plan"), pursuant to which Suburban Bancshares would merge with
and into Columbia Bancorp (the "Holding Company Merger"), with shares of the
Common Stock of Columbia Bancorp to be issued to the stockholders of Suburban
Bancshares; and

     WHEREAS, pursuant to Section 6.10 of the Plan, Columbia Bancorp has
covenanted to obtain agreements from each of its officers and directors (and to
use commercially reasonable efforts to obtain agreements from any such other
person identified herein as a Columbia Bancorp Stockholder) in which the
officers and directors of Columbia Bancorp (in their capacity as Columbia
Bancorp Stockholders) and the Columbia Bancorp Stockholders would agree to
support the Holding Company Merger; and the Columbia Bancorp Stockholders have
in accordance with such covenant agreed to support the Holding Company Merger.

     NOW, THEREFORE, to induce Columbia Bancorp to enter into the Plan and in
consideration of the mutual covenants and agreements set forth herein and in the
Plan and the mutual benefits to be derived herefrom and therefrom, the parties
agree as follows:

     1.  Representations of the Columbia Bancorp Stockholders.  Each of the
Columbia Bancorp Stockholders, severally, and not jointly, represents that:

                                      B-2
<PAGE>

        (a)(1)  such Columbia Bancorp Stockholder possesses the sole or joint
right to vote, or direct the voting of, all of the Shares set forth on Schedule
A opposite the Columbia Bancorp Stockholder's name, (2) such number of Shares
constitutes all of the Shares with respect to which the Columbia Bancorp
Stockholder possesses the sole or joint right to vote, or direct the voting of,
as the case may be, and (3) except as to Shares held only under a power of
attorney or as guardian or custodian, such Columbia Bancorp Stockholder has good
and merchantable title to all of the Shares indicated on said list opposite the
Columbia Bancorp Stockholder's name, free of all restrictions and encumbrances
of every kind and character, except as indicated on Schedule A.

        (b)(1)  such Columbia Bancorp Stockholder possesses the sole or joint
power to dispose of, or direct the disposition of, the Shares set forth on
Schedule A opposite the Columbia Bancorp Stockholder's name, (2) such number of
Shares constitutes all of the Shares with respect to which the Columbia Bancorp
Stockholder possesses or will possess the sole or joint power to dispose of or
direct the disposition of, and (3) except as to Shares held only under a power
of attorney, such Columbia Bancorp Stockholder has good and merchantable title
to all of the Shares indicated on said list opposite the Columbia Bancorp
Stockholder's name free of all restrictions and encumbrances of any kind or
character except as indicated on Schedule A.

        (c)  such Columbia Bancorp Stockholder does not own, of record or
beneficially, any Shares that are not reflected on Schedule A. For the purposes
of this Agreement, beneficial ownership has the meaning set forth in Rule 13d-3
of the Securities Exchange Act of 1934, as amended.

        (d)  such Columbia Bancorp Stockholder has full right, power, and
authority to enter into, deliver and perform this Agreement; this Agreement has
been duly executed and delivered by such Columbia Bancorp Stockholder; and this
Agreement constitutes the legal, valid, and binding obligation of the Columbia
Bancorp Stockholder, and is enforceable in accordance with its terms.

  2.  Covenants of the Columbia Bancorp Stockholders.  Each of the Columbia
Bancorp Stockholders, severally and not jointly, covenants as follows:

        (a)  Restrictions on Transfer.  With respect to Shares listed on
  Schedule A, during the term of this Agreement, such Columbia Bancorp
  Stockholder shall not voluntarily pledge, hypothecate, grant a security
  interest in, sell, transfer, or otherwise dispose of or encumber any of such
  Shares and will not enter into any agreement, arrangement, or understanding
  (other than a proxy for the purpose of voting his or her Shares in accordance
  with Subparagraph 2(c) hereof) which would, during that term (i) restrict,
  (ii) establish a right of first refusal to, or (iii) otherwise relate to the
  transfer or voting of such Shares; provided, however, this

                                      B-3
<PAGE>

  restriction shall not apply to a transfer of any of the Shares by the Columbia
  Bancorp Stockholder to his or her spouse, children, or grandchildren, subject
  to the conditions that any transferee, recipient, or custodian of any such
  transferee or recipient must execute an agreement substantially in the form of
  this Agreement in a form satisfactory to Columbia Bancorp, and Schedule A
  hereto may be revised by Columbia Bancorp to reflect such transfer.

     (b)  Other Restrictions.  During the term of this Agreement, such Columbia
  Bancorp Stockholder, as a Columbia Bancorp Stockholder, shall not, directly or
  indirectly, solicit, initiate, or encourage inquiries or proposals from, or
  participate in any discussions or negotiations with, or provide any
  information to, any individual, corporation, partnership, or other person,
  entity, or group (other than Suburban Bancshares, any of its subsidiaries, and
  their respective officers, employees, representatives, and agents) concerning
  any sale of assets, sale of shares of capital stock, merger, consolidation,
  share exchange, or similar transactions involving Columbia Bancorp. Such
  Columbia Bancorp Stockholder shall promptly advise Suburban Bancshares of, and
  communicate to Suburban Bancshares the terms of, any such inquiry or proposal
  addressed either to such Columbia Bancorp Stockholder or to Columbia Bancorp
  that such Columbia Bancorp Stockholder receives or of which such Columbia
  Bancorp Stockholder has knowledge.

     (c)  Holding Company Merger.  With respect to the Shares listed on Schedule
  A pursuant to Subparagraph 1(a) hereof, each of the Columbia Bancorp
  Stockholders shall vote such Shares to ratify and confirm the Plan and the
  Holding Company Merger and the transactions contemplated thereby. Each of the
  Columbia Bancorp Stockholders, as a Columbia Bancorp Stockholder, further
  agrees to use all commercially reasonable efforts to cause the Holding Company
  Merger to be effected.

     (d)  Additional Shares.  The provisions of subparagraphs (a) and (c) above
  shall apply to all Shares currently owned and hereafter acquired, of record or
  beneficially, by each of the Columbia Bancorp Stockholders.

  3.  Termination.  This Agreement shall terminate upon the termination of the
Plan.

  4.  Governing Law.  This Agreement shall in all respects be governed by and
construed under the laws of Maryland, all rights and remedies being governed by
such laws.

  5.  Benefit of Agreement.  This Agreement shall be binding upon and inure to
the benefit of, and shall be enforceable by, the parties hereto and their
respective personal representatives, successors, and assigns, except that
neither party may transfer or assign any of its respective rights or obligations
hereunder without the prior written consent of the other party or, if by
Columbia Bancorp, in accordance with the Plan.

                                      B-4
<PAGE>

  6.  Counterparts.  For convenience of the parties hereto, this Agreement may
be executed in several counterparts, each of which shall be deemed an original,
all of which together shall constitute one and the same instrument.

  IN WITNESS WHEREOF, Suburban Bancshares, Inc. and the Columbia Bancorp
Stockholders have caused this Agreement to be duly executed as of the day and
year first above written.

                                   SUBURBAN BANCSHARES, INC.



                                   By:_________________________________
                                      Winfield M. Kelly, Jr.
                                      Chairman of the Board
                                      and Chief Executive Officer


                                   COLUMBIA BANCORP STOCKHOLDERS:

                                   ____________________________________

                                   ____________________________________

                                   ____________________________________

                                   ____________________________________

                                   ____________________________________

                                      B-5
<PAGE>

                                   APPENDIX C

                    SUPPORT AGREEMENT OF SUBURBAN BANCSHARES

                                      C-1
<PAGE>

                           FORM OF SUPPORT AGREEMENT

     THIS SUPPORT AGREEMENT (this "Agreement") dated as of September 28, 1999,
between COLUMBIA BANCORP, a Maryland corporation and registered bank holding
company ("Columbia Bancorp"), and each of the individuals listed on Schedule A
attached hereto (collectively, the "Suburban Bancshares Stockholders").

                             W I T N E S S E T H:

     WHEREAS, the Suburban Bancshares Stockholders (i) collectively possess the
sole or joint right to vote, or direct the voting of, an aggregate of
___________ shares of common stock, par value $.01 per share (the "Shares"), of
Suburban Bancshares, Inc., a Delaware corporation and registered bank holding
company ("Suburban Bancshares"), which constitute approximately _____ % of the
outstanding capital stock of Suburban Bancshares, and (ii) individually possess
the right to vote, or to direct the voting of, the number of Shares set forth
opposite such Suburban Bancshares Stockholder's name on Schedule A hereto; and

     WHEREAS, the Suburban Bancshares Stockholders (i) collectively possess the
sole or joint power to dispose of, or to direct the disposition of, an aggregate
of ___________ Shares, which constitute approximately _____ % of the outstanding
capital stock of Suburban Bancshares, and (ii) individually possess the power to
dispose of, or direct the disposition of, the number of Shares set forth
opposite such Suburban Bancshares Stockholder's name on Schedule A hereto; and

     WHEREAS, Columbia Bancorp has entered into a Plan and Agreement to Merge
with Suburban Bancshares, dated as of the business day immediately prior to the
date hereof (the "Plan"), pursuant to which Suburban Bancshares would merge with
and into Columbia Bancorp (the "Holding Company Merger"), with shares of the
Common Stock of Columbia Bancorp to be issued to the stockholders of Suburban
Bancshares; and

     WHEREAS, pursuant to Section 5.10 of the Plan, Suburban Bancshares has
covenanted to obtain agreements from each of its officers and directors (and to
use commercially reasonable efforts to obtain agreements from any such other
person identified herein as a Suburban Bancshares Stockholder) in which the
officers and directors of Suburban Bancshares (in their capacity as Suburban
Bancshares Stockholders) and the Suburban Bancshares Stockholders would agree to
support the Holding Company Merger; and the Suburban Bancshares Stockholders
have in accordance with such covenant agreed to support the Holding Company
Merger.

     NOW, THEREFORE, to induce Columbia Bancorp to enter into the Plan and in
consideration of the mutual covenants and agreements set forth herein and in the
Plan and the mutual benefits to be derived herefrom and therefrom, the parties
agree as follows:

                                      C-2
<PAGE>

     1.   Representations of the Suburban Bancshares Stockholders.  Each of the
Suburban Bancshares Stockholders, severally, and not jointly, represents that:

          (a)(1) such Suburban Bancshares Stockholder possesses the sole or
     joint right to vote, or direct the voting of, all of the Shares set forth
     on Schedule A opposite the Suburban Bancshares Stockholder's name, (2) such
     number of Shares constitutes all of the Shares with respect to which the
     Suburban Bancshares Stockholder possesses the sole or joint right to vote,
     or direct the voting of, as the case may be, and (3) except as to Shares
     held only under a power of attorney or as guardian or custodian, such
     Suburban Bancshares Stockholder has good and merchantable title to all of
     the Shares indicated on said list opposite the Suburban Bancshares
     Stockholder's name, free of all restrictions and encumbrances of every kind
     and character, except as indicated on Schedule A.

          (b)(1) such Suburban Bancshares Stockholder possesses the sole or
     joint power to dispose of, or direct the disposition of, the Shares set
     forth on Schedule A opposite the Suburban Bancshares Stockholder's name,
     (2) such number of Shares constitutes all of the Shares with respect to
     which the Suburban Bancshares Stockholder possesses or will possess the
     sole or joint power to dispose of or direct the disposition of, and (3)
     except as to Shares held only under a power of attorney, such Suburban
     Bancshares Stockholder has good and merchantable title to all of the Shares
     indicated on said list opposite the Suburban Bancshares Stockholder's name
     free of all restrictions and encumbrances of any kind or character except
     as indicated on Schedule A.

          (c)  such Suburban Bancshares Stockholder does not own, of record or
     beneficially, any Shares that are not reflected on Schedule A. For the
     purposes of this Agreement, beneficial ownership has the meaning set forth
     in Rule 13d-3 of the Securities Exchange Act of 1934, as amended.

          (d)  such Suburban Bancshares Stockholder has full right, power, and
     authority to enter into, deliver and perform this Agreement; this Agreement
     has been duly executed and delivered by such Suburban Bancshares
     Stockholder; and this Agreement constitutes the legal, valid, and binding
     obligation of the Suburban Bancshares Stockholder, and is enforceable in
     accordance with its terms.

     2.   Covenants of the Suburban Bancshares Stockholders. Each of the
Suburban Bancshares Stockholders, severally and not jointly, covenants as
follows:

          (a)  Restrictions on Transfer. With respect to Shares listed on
     Schedule A, during the term of this Agreement, such Suburban Bancshares
     Stockholder shall not voluntarily pledge, hypothecate, grant a security
     interest in, sell, transfer, or otherwise dispose of or encumber any of
     such Shares and will not enter into

                                      C-3
<PAGE>

     any agreement, arrangement, or understanding (other than a proxy for the
     purpose of voting his or her Shares in accordance with Subparagraph 2(c)
     hereof) which would, during that term (i) restrict, (ii) establish a right
     of first refusal to, or (iii) otherwise relate to the transfer or voting of
     such Shares; provided, however, this restriction shall not apply to a
     transfer of any of the Shares by the Suburban Bancshares Stockholder to his
     or her spouse, children, or grandchildren, subject to the conditions that
     any transferee, recipient, or custodian of any such transferee or recipient
     must execute an agreement substantially in the form of this Agreement in a
     form satisfactory to Columbia Bancorp, and Schedule A hereto may be revised
     by Columbia Bancorp to reflect such transfer.

          (b) Other Restrictions. During the term of this Agreement, such
     Suburban Bancshares Stockholder, as a Suburban Bancshares Stockholder,
     shall not, directly or indirectly, solicit, initiate, or encourage
     inquiries or proposals from, or participate in any discussions or
     negotiations with, or provide any information to, any individual,
     corporation, partnership, or other person, entity, or group (other than
     Columbia Bancorp, any of its subsidiaries, and their respective officers,
     employees, representatives, and agents) concerning any sale of assets, sale
     of shares of capital stock, merger, consolidation, share exchange, or
     similar transactions involving Suburban Bancshares. Such Suburban
     Bancshares Stockholder shall promptly advise Columbia Bancorp of, and
     communicate to Columbia Bancorp the terms of, any such inquiry or proposal
     addressed either to such Suburban Bancshares Stockholder or to Suburban
     Bancshares that such Suburban Bancshares Stockholder receives or of which
     such Suburban Bancshares Stockholder has knowledge.

          (c) Holding Company Merger. With respect to the Shares listed on
     Schedule A pursuant to Subparagraph 1(a) hereof, each of the Suburban
     Bancshares Stockholders shall vote such Shares to ratify and confirm the
     Plan and the Holding Company Merger and the transactions contemplated
     thereby. Each of the Suburban Bancshares Stockholders, as a Suburban
     Bancshares Stockholder, further agrees to use all commercially reasonable
     efforts to cause the Mergers to be effected.

          (d) Additional Shares. The provisions of subparagraphs (a) and (c)
     above shall apply to all Shares currently owned and hereafter acquired, of
     record or beneficially, by each of the Suburban Bancshares Stockholders.

     3.  Termination. This Agreement shall terminate upon the termination of the
         Plan.

     4.  Governing Law. This Agreement shall in all respects be governed by and
construed under the laws of Maryland, all rights and remedies being governed by
such laws.

                                      C-4
<PAGE>

     5. Benefit of Agreement. This Agreement shall be binding upon and inure to
the benefit of, and shall be enforceable by, the parties hereto and their
respective personal representatives, successors, and assigns, except that
neither party may transfer or assign any of its respective rights or obligations
hereunder without the prior written consent of the other party or, if by
Columbia Bancorp, in accordance with the Plan.

     6. Counterparts.  For convenience of the parties hereto, this Agreement may
be executed in several counterparts, each of which shall be deemed an original,
all of which together shall constitute one and the same instrument.

     IN WITNESS WHEREOF, Columbia Bancorp and the Suburban Bancshares
Stockholders have caused this Agreement to be duly executed as of the day and
year first above written.

                                 COLUMBIA BANCORP



                                 By:_____________________________________
                                    John M. Bond, Jr.
                                    President and Chief Executive Officer


                                 SUBURBAN BANCSHARES STOCKHOLDERS:


                                 ________________________________________



                                 ________________________________________



                                 ________________________________________



                                 ________________________________________

                                      C-5
<PAGE>

                                  APPENDIX D

                    COLUMBIA BANCORP STOCK OPTION AGREEMENT

                                      D-1
<PAGE>

                        FORM OF STOCK OPTION AGREEMENT

     This STOCK OPTION AGREEMENT (this "Option Agreement") dated as of September
28, 1999, between SUBURBAN BANCSHARES, INC. ("Suburban Bancshares"), a Delaware
corporation, and COLUMBIA BANCORP ("Columbia Bancorp"), a Maryland corporation,
recites and provides:

     A.  The Board of Directors of Suburban Bancshares and Columbia Bancorp have
approved a Plan and Agreement to Merge dated September 28, 1999 (the "Plan")
providing for the merger (the "Holding Company Merger") of Suburban Bancshares
with and into Columbia Bancorp.

     B.  As a condition to and as consideration for Suburban Bancshares' entry
into the Plan and to induce such entry, Columbia Bancorp has agreed to grant to
Suburban Bancshares the option set forth herein to purchase authorized but
unissued shares of Columbia Bancorp Common Stock.

     NOW, THEREFORE, the parties agree as follows:

     1.  Definitions.  Capitalized terms defined in the Plan and used herein
shall have the same meanings as in the Plan.

     2.  Grant of Option.  Subject to the terms and conditions set forth herein,
Columbia Bancorp hereby grants to Suburban Bancshares an option (the "Option")
to purchase up to 497,140 shares of Columbia Bancorp Common Stock at an exercise
price of $13.063 per share payable in cash as provided in Section 4; provided,
however, that in the event Columbia Bancorp issues or agrees to issue any shares
of Columbia Bancorp Common Stock (other than as permitted under the Plan) at a
price less than $13.063 per share (as adjusted pursuant to Section 6), the
exercise price shall be such lesser price.

     3.  Exercise of Option.  (a)  Unless Suburban Bancshares shall have
breached in any material respect any covenant or representation contained in the
Plan and such breach has not been cured, Suburban Bancshares may exercise the
Option, in whole or part, at any time or from time to time if a Purchase Event
(as defined below) shall have occurred and be continuing; provided, that to the
extent the Option shall not have been exercised, it shall terminate and be of no
further force and effect upon the earliest to occur of (i) the Effective Date of
the Holding Company Merger, or (ii) the termination of the Plan in accordance
with the provisions thereof prior to the occurrence of a Purchase Event (other
than as a result of a willful breach by Columbia Bancorp of any Specified
Covenant or as a result of failure of Columbia Bancorp's stockholders to approve
the Plan by the vote required under applicable law or under Columbia Bancorp's
Charter), or (iii) 12 months after termination of the Plan due to a willful
breach by Columbia Bancorp of any Specified Covenant or failure of Columbia
Bancorp's stockholders to approve the Plan by the vote required under applicable
law or under Columbia Bancorp's

                                      D-2
<PAGE>

Charter; provided, however, that any purchase of shares upon exercise of the
Option shall be subject to compliance with applicable law, including, without
limitation, the Bank Holding Company Act of 1956, as amended. Any exercise of
the Option shall be subject to compliance with applicable provisions of law.

          (b)  As used herein, a "Purchase Event" shall mean any of the
following events or transactions occurring after the date hereof:

               (i)   Columbia Bancorp or The Columbia Bank ("Columbia Bank"),
     without having received Suburban Bancshares' prior written consent, shall
     have entered into an agreement with any person (x) to merge or consolidate,
     or enter into any similar transaction, except as contemplated in the Plan,
     (y) to purchase, lease, or otherwise acquire all or substantially all of
     the assets of Columbia Bancorp or Columbia Bank, or (z) to purchase or
     otherwise acquire (including by way of merger, consolidation, share
     exchange, or any similar transaction) securities representing 15% or more
     of the voting power of Columbia Bancorp or Columbia Bank;

               (ii)  any person (other than Columbia Bancorp or Columbia Bank in
     a fiduciary capacity, or Suburban Bancshares or Columbia Bank in a
     fiduciary capacity) shall have acquired beneficial ownership or the right
     to acquire beneficial ownership of 15% or more of the outstanding shares of
     Columbia Bancorp Common Stock after the date hereof (the term "beneficial
     ownership" for purposes of this Option Agreement having the meaning
     assigned thereto in Section 13(d) of the Securities Exchange Act of 1934
     (the "Exchange Act") and the regulations promulgated thereunder);

               (iii) any person shall have made a bona fide proposal to Columbia
     Bancorp by public announcement or written communication that is or becomes
     the subject of public disclosure to acquire Columbia Bancorp or Columbia
     Bank by merger, consolidation, purchase of all or substantially all of its
     assets, or any other similar transaction, and following such bona fide
     proposal the stockholders of Columbia Bancorp vote not to adopt the Plan;
     or

               (iv)  Columbia Bancorp shall have willfully breached any
     Specified Covenant following a bona fide proposal to Columbia Bancorp or
     Columbia Bank to acquire Columbia Bancorp or Columbia Bank by merger,
     consolidation, purchase of all or substantially all of its assets, or any
     other similar transaction, which breach would entitle Suburban Bancshares
     to terminate the Plan (without regard to the cure periods provided for
     therein) and such breach shall not have been cured prior to the Notice Date
     (as defined below).

               If more than one of the transactions giving rise to a Purchase
     Event under this Section 3(b) is undertaken or effected, then all such
     transactions shall give rise only to one Purchase Event, which Purchase
     Event shall be deemed continuing for all purposes hereunder until all such
     transactions are abandoned.

                                      D-3
<PAGE>

     As used in this Option Agreement, "person" shall have the meanings
     specified in Sections 3(a)(9) and 13(d)(3) of the Exchange Act.

          (c)  In the event Suburban Bancshares wishes to exercise the Option,
it shall send to Columbia Bancorp a written notice (the date of which being
herein referred to as the "Notice Date") specifying (i) the total number of
shares it will purchase pursuant to such exercise, and (ii) a place and date not
earlier than three business days nor later than 60 business days after the
Notice Date for the closing of such purchase ("Closing Date"); provided, that if
prior notification to or approval of any federal or state regulatory agency is
required in connection with such purchase, Suburban Bancshares shall promptly
file the required notice or application for approval and shall expeditiously
process the same and the period of time that otherwise would run pursuant to
this sentence shall run instead from the date on which any required notification
period has expired or been terminated or such approval has been obtained and any
requisite waiting period shall have passed.

          (d)  As used herein, "Specified Covenant" means any covenant made by
Columbia Bancorp and contained in Section 6 of the Plan.

     4. Payment and Delivery of Certificates.  (a)  At the closing referred to
in Section 3, Suburban Bancshares shall pay to Columbia Bancorp the aggregate
purchase price for the shares of Columbia Bancorp Common Stock purchased
pursuant to the exercise of the Option in immediately available funds by a wire
transfer to a bank account designated by Columbia Bancorp.

          (b)  At such closing, simultaneously with the delivery of funds as
provided in subsection (a), Columbia Bancorp shall deliver to Suburban
Bancshares a certificate or certificates representing the number of shares of
Columbia Bancorp Common Stock purchased by Suburban Bancshares, and Suburban
Bancshares shall deliver to Columbia Bancorp a letter agreeing that Suburban
Bancshares will not offer to sell or otherwise dispose of such shares in
violation of applicable law or the provisions of this Option Agreement.

          (c)  Certificates for Columbia Bancorp Common Stock delivered at a
closing hereunder shall be endorsed with a restrictive legend which shall read
substantially as follows:

     "THE TRANSFER OF THE SHARES REPRESENTED BY THIS CERTIFICATE IS SUBJECT TO
     CERTAIN PROVISIONS OF A STOCK OPTION AGREEMENT BETWEEN THE REGISTERED
     HOLDER HEREOF AND COLUMBIA BANCORP ("COLUMBIA BANCORP") AND TO RESALE
     RESTRICTIONS ARISING UNDER THE SECURITIES ACT OF 1933, AS AMENDED, A COPY
     OF WHICH AGREEMENT IS ON FILE AT THE PRINCIPAL OFFICE OF COLUMBIA BANCORP.
     A COPY OF SUCH AGREEMENT WILL BE PROVIDED TO THE HOLDER HEREOF WITHOUT
     CHARGE UPON RECEIPT BY COLUMBIA BANCORP OF A WRITTEN REQUEST."

                                      D-4
<PAGE>

          It is understood and agreed that the above legend shall be removed by
delivery of substitute certificate(s) without such legend if Suburban Bancshares
shall have delivered to Columbia Bancorp a copy of a letter from the staff of
the Securities and Exchange Commission, or an opinion of counsel, in form and
substance satisfactory to Columbia Bancorp, to the effect that such legend is
not required for purposes of the Securities Act of 1933, as amended (the
"Securities Act").

     5. Representations.  Columbia Bancorp represents, warrants, and covenants
to Suburban Bancshares as follows:

          (a)  Columbia Bancorp shall at all times maintain sufficient
authorized but unissued shares of Columbia Bancorp Common Stock so that the
Option may be exercised without authorization of additional shares of Columbia
Bancorp Common Stock.

          (b)  The shares to be issued upon due exercise, in whole or in part,
of the Option, when paid for as provided herein, will be duly authorized,
validly issued, fully paid, and nonassessable.

     6. Adjustment Upon Changes in Capitalization.  In the event of any change
in Columbia Bancorp Common Stock by reason of stock dividends, split-ups,
mergers, recapitalizations, combinations, exchanges of shares, or the like, the
type and number of shares subject to the Option, and the purchase price per
share, as the case may be, shall be adjusted appropriately.  In the event that
any additional shares of Columbia Bancorp Common Stock are issued or otherwise
become outstanding after the date of this Option Agreement (other than pursuant
to this Option Agreement), the number of shares of Columbia Bancorp Common Stock
subject to the Option shall be adjusted so that, after such issuance, it equals
9.936% of the number of shares of Columbia Bancorp Common Stock then issued and
outstanding without giving effect to any shares subject or issued pursuant to
the Option.  Nothing contained in this Section 6 shall be deemed to authorize
Columbia Bancorp to breach any provision of the Plan.

     7. Registration Rights.  If requested by Suburban Bancshares, Columbia
Bancorp shall as expeditiously as possible file a registration statement on a
form of general use under the Securities Act if necessary in order to permit the
sale or other disposition of the shares of Columbia Bancorp Common Stock that
have been acquired upon exercise of the Option in accordance with the intended
method of sale or other disposition requested by Suburban Bancshares.  Suburban
Bancshares shall provide all information reasonably requested by Columbia
Bancorp for inclusion in any registration statement to be filed hereunder.
Columbia Bancorp will use its best efforts to cause such registration statement
first to become effective and then to remain effective for such period not in
excess of 270 days from the day such registration statement first becomes
effective as may be reasonably necessary to effect such sales or other
dispositions.  Only one registration may be effected under this Section 7 at
Columbia Bancorp's expense, and which shall not include underwriting commissions
and the fees and disbursements of Suburban Bancshares' counsel attributable to
the registration of such Columbia Bancorp Common Stock.  The filing of any
registration statement hereunder may be delayed for such

                                      D-5
<PAGE>

period of time as may reasonably be required to facilitate any public
distribution by Columbia Bancorp of Columbia Bancorp Common Stock. If requested
by Suburban Bancshares, in connection with any such registration, Columbia
Bancorp will become a party to any underwriting agreement relating to the sale
of such shares, but only to the extent of obligating itself in respect of
representations, warranties, indemnities, and other agreements customarily
included in such underwriting agreements. Upon receiving any request from
Suburban Bancshares or assignee thereof under this Section 7, Columbia Bancorp
agrees to send a copy thereof to Suburban Bancshares and to any assignee thereof
known to Columbia Bancorp, in each case by promptly mailing the same, postage
prepaid, to the address of record of the persons entitled to receive such
copies.

     8.  Severability. If any term, provision, covenant, or restriction
contained in this Option Agreement is held by a court or a federal or state
regulatory agency of competent jurisdiction to be invalid, void, or
unenforceable, the remainder of the terms, provisions, and covenants, and
restrictions contained in this Option Agreement shall remain in full force and
effect, and shall in no way be affected, impaired, or invalidated. If for any
reason such court or regulatory agency determines that the Option will not
permit the holder to acquire the full number of shares of Columbia Bancorp
Common Stock provided in Section 2 (as adjusted pursuant to Section 6), it is
the express intention of Columbia Bancorp to allow the holder to acquire such
lesser number of shares as may be permissible, without any amendment or
modification hereof.

     9.  Miscellaneous.

           (a)  Expenses.  Except as otherwise provided herein, each of the
parties hereto shall bear and pay all costs and expenses incurred by it or on
its behalf in connection with the transactions contemplated hereunder, including
fees and expenses of its own financial consultants, investment bankers,
accountants, and counsel.

           (b)  Entire Agreement. Except as otherwise expressly provided herein,
this Option Agreement contains the entire agreement between the parties with
respect to the transactions contemplated hereunder and supersedes all prior
arrangements or understandings with respect thereto, written or oral. The terms
and conditions of this Option Agreement shall inure to the benefit of and be
binding upon the parties hereto and their respective successors and assigns.
Nothing in this Option Agreement, expressed or implied, is intended to confer
upon any party, other than the parties hereto, and their respective successors
and assigns, any rights, remedies, obligations or liabilities under or by reason
of this Option Agreement, except as expressly provided herein.

           (c)  Assignment.  Neither of the parties hereto may assign any of its
rights or obligations under this Option Agreement or the Option created
hereunder to any other person, without the express written consent of the other
party, except that in the event a Purchase Event shall have occurred and be
continuing Suburban Bancshares may assign in whole or in part its rights and
obligations hereunder; provided, however, that to the extent required by
applicable regulatory authorities, Suburban Bancshares may not assign its rights
under the Option except in

                                      D-6
<PAGE>

(i) a widely dispersed public distribution, (ii) a private placement in which no
one party acquires the right to purchase in excess of 2% of the voting shares of
Columbia Bancorp, (iii) an assignment to a single party (e.g., a broker or
investment banker) for the purpose of conducting a widely dispersed public
distribution on Suburban Bancshares' behalf, or (iv) any other manner approved
by applicable regulatory authorities.

          (d)  Notices.  All notices or other communications which are required
or permitted hereunder shall be in writing and sufficient if delivered in the
manner and to the address provided for in or pursuant to Section 15 of the Plan.

          (e)  Counterparts.  This Option Agreement may be executed in any
number of counterparts, and each such counterpart shall be deemed to be an
original instrument, but all such counterparts together shall constitute but one
agreement.

          (f)  Specific Performance.  The parties agree that damages would be an
inadequate remedy for a breach of the provisions of this Option Agreement by
either party hereto and that this Option Agreement may be enforced by either
party hereto through injunctive or other equitable relief.

          (g)  Governing Law.  This Option Agreement shall be governed by and
construed in accordance with the laws of the State of Maryland applicable to
agreements made and entirely to be performed within such state and such federal
laws as may be applicable.

                                      D-7
<PAGE>

     IN WITNESS WHEREOF, each of the parties hereto has executed this Option
Agreement as of the day and year first written above.


                              SUBURBAN BANCSHARES, INC.


                              By:___________________________________
                                 Winfield M. Kelly, Jr.
                                 Chairman of the Board
                                 and Chief Executive Officer


                              COLUMBIA BANCORP


                              By:___________________________________
                                 John M. Bond, Jr.
                                 President and Chief Executive Officer

                                      D-8
<PAGE>

                                   APPENDIX E

                   SUBURBAN BANCSHARES STOCK OPTION AGREEMENT

                                      E-1
<PAGE>

                         FORM OF STOCK OPTION AGREEMENT

     This STOCK OPTION AGREEMENT (this "Option Agreement") dated as of September
28, 1999, between SUBURBAN BANCSHARES, INC. ("Suburban Bancshares"), a Delaware
corporation, and COLUMBIA BANCORP ("Columbia Bancorp"), a Maryland corporation,
recites and provides:

     A.  The Board of Directors of Suburban Bancshares and Columbia Bancorp have
approved a Plan and Agreement to Merge dated September 28, 1999 (the "Plan")
providing for the merger (the "Holding Company Merger") of Suburban Bancshares
with and into Columbia Bancorp.

     B.  As a condition to and as consideration for Columbia Bancorp's entry
into the Plan and to induce such entry, Suburban Bancshares has agreed to grant
to Columbia Bancorp the option set forth herein to purchase authorized but
unissued shares of Suburban Bancshares Common Stock.

     NOW, THEREFORE, the parties agree as follows:

     1.  Definitions.  Capitalized terms defined in the Plan and used herein
shall have the same meanings as in the Plan.

     2.  Grant of Option.  Subject to the terms and conditions set forth herein,
Suburban Bancshares hereby grants to Columbia Bancorp an option (the "Option")
to purchase up to 2,807,668 shares of Suburban Bancshares Common Stock at an
exercise price of $2.313 per share payable in cash as provided in Section 4;
provided, however, that in the event Suburban Bancshares issues or agrees to
issue any shares of Suburban Bancshares Common Stock (other than as permitted
under the Plan) at a price less than $2.313 per share (as adjusted pursuant to
Section 6), the exercise price shall be such lesser price.

     3.  Exercise of Option.  (a)  Unless Columbia Bancorp shall have breached
in any material respect any covenant or representation contained in the Plan and
such breach has not been cured, Columbia Bancorp may exercise the Option, in
whole or part, at any time or from time to time if a Purchase Event (as defined
below) shall have occurred and be continuing; provided, that to the extent the
Option shall not have been exercised, it shall terminate and be of no further
force and effect upon the earliest to occur of (i) the Effective Date of the
Holding Company Merger, or (ii) the termination of the Plan in accordance with
the provisions thereof prior to the occurrence of a Purchase Event (other than
as a result of a willful breach by Suburban Bancshares of any Specified Covenant
or as a result of failure of Suburban Bancshares' stockholders to approve the
Plan by the vote required under applicable law or under Suburban Bancshares'
Charter), or (iii) 12 months after termination of the Plan due to a willful
breach by Suburban Bancshares of any Specified Covenant or failure of Suburban
Bancshares' stockholders to approve the Plan by the vote required under
applicable law or under Suburban

                                      E-2
<PAGE>

Bancshares' Charter; provided, however, that any purchase of shares upon
exercise of the Option shall be subject to compliance with applicable law,
including, without limitation, the Bank Holding Company Act of 1956, as amended.
Any exercise of the Option shall be subject to compliance with applicable
provisions of law.

          (b)  As used herein, a "Purchase Event" shall mean any of the
following events or transactions occurring after the date hereof:

          (i)  Suburban Bancshares or Suburban Bank of Maryland ("Suburban
     Bank"), without having received Columbia Bancorp's prior written consent,
     shall have entered into an agreement with any person (x) to merge or
     consolidate, or enter into any similar transaction, except as contemplated
     in the Plan, (y) to purchase, lease, or otherwise acquire all or
     substantially all of the assets of Suburban Bancshares or Suburban Bank, or
     (z) to purchase or otherwise acquire (including by way of merger,
     consolidation, share exchange, or any similar transaction) securities
     representing 15% or more of the voting power of Suburban Bancshares or
     Suburban Bank;

          (ii)  any person (other than Suburban Bancshares or Suburban Bank in a
     fiduciary capacity, or Columbia Bancorp or Columbia Bank in a fiduciary
     capacity) shall have acquired beneficial ownership or the right to acquire
     beneficial ownership of 15% or more of the outstanding shares of Suburban
     Bancshares Common Stock after the date hereof (the term "beneficial
     ownership" for purposes of this Option Agreement having the meaning
     assigned thereto in Section 13(d) of the Securities Exchange Act of 1934
     (the "Exchange Act") and the regulations promulgated thereunder);

          (iii)  any person shall have made a bona fide proposal to Suburban
     Bancshares by public announcement or written communication that is or
     becomes the subject of public disclosure to acquire Suburban Bancshares or
     Suburban Bank by merger, consolidation, purchase of all or substantially
     all of its assets, or any other similar transaction, and following such
     bona fide proposal the stockholders of Suburban Bancshares vote not to
     adopt the Plan; or

          (iv)  Suburban Bancshares shall have willfully breached any Specified
     Covenant following a bona fide proposal to Suburban Bancshares or Suburban
     Bank to acquire Suburban Bancshares or Suburban Bank by merger,
     consolidation, purchase of all or substantially all of its assets, or any
     other similar transaction, which breach would entitle Columbia Bancorp to
     terminate the Plan (without regard to the cure periods provided for
     therein) and such breach shall not have been cured prior to the Notice Date
     (as defined below).

If more than one of the transactions giving rise to a Purchase Event under this
Section 3(b) is undertaken or effected, then all such transactions shall give
rise only to one Purchase Event, which Purchase Event shall be deemed continuing
for all purposes hereunder until all such

                                      E-3
<PAGE>

transactions are abandoned. As used in this Option Agreement, "person" shall
have the meanings specified in Sections 3(a)(9) and 13(d)(3) of the Exchange
Act.

          (c)  In the event Columbia Bancorp wishes to exercise the Option, it
shall send to Suburban Bancshares a written notice (the date of which being
herein referred to as the "Notice Date") specifying (i) the total number of
shares it will purchase pursuant to such exercise, and (ii) a place and date not
earlier than three business days nor later than 60 business days after the
Notice Date for the closing of such purchase ("Closing Date"); provided, that if
prior notification to or approval of any federal or state regulatory agency is
required in connection with such purchase, Columbia Bancorp shall promptly file
the required notice or application for approval and shall expeditiously process
the same and the period of time that otherwise would run pursuant to this
sentence shall run instead from the date on which any required notification
period has expired or been terminated or such approval has been obtained and any
requisite waiting period shall have passed.

          (d)  As used herein, "Specified Covenant" means any covenant made by
Suburban Bancshares and contained in Section 5 of the Plan.

     4.  Payment and Delivery of Certificates.  (a)  At the closing referred to
in Section 3, Columbia Bancorp shall pay to Suburban Bancshares the aggregate
purchase price for the shares of Suburban Bancshares Common Stock purchased
pursuant to the exercise of the Option in immediately available funds by a wire
transfer to a bank account designated by Suburban Bancshares.

          (b)  At such closing, simultaneously with the delivery of funds as
provided in subsection (a), Suburban Bancshares shall deliver to Columbia
Bancorp a certificate or certificates representing the number of shares of
Suburban Bancshares Common Stock purchased by Columbia Bancorp, and Columbia
Bancorp shall deliver to Suburban Bancshares a letter agreeing that Columbia
Bancorp will not offer to sell or otherwise dispose of such shares in violation
of applicable law or the provisions of this Option Agreement.

          (c)  Certificates for Suburban Bancshares Common Stock delivered at a
closing hereunder shall be endorsed with a restrictive legend which shall read
substantially as follows:

     "THE TRANSFER OF THE SHARES REPRESENTED BY THIS CERTIFICATE IS SUBJECT TO
     CERTAIN PROVISIONS OF A STOCK OPTION AGREEMENT BETWEEN THE REGISTERED
     HOLDER HEREOF AND SUBURBAN BANCSHARES, INC. ("SUBURBAN BANCSHARES") AND TO
     RESALE RESTRICTIONS ARISING UNDER THE SECURITIES ACT OF 1933, AS AMENDED, A
     COPY OF WHICH AGREEMENT IS ON FILE AT THE PRINCIPAL OFFICE OF SUBURBAN
     BANCSHARES. A COPY OF SUCH AGREEMENT WILL BE PROVIDED TO THE HOLDER HEREOF
     WITHOUT CHARGE UPON RECEIPT BY SUBURBAN BANCSHARES OF A WRITTEN REQUEST."

                                      E-4
<PAGE>

          It is understood and agreed that the above legend shall be removed by
delivery of substitute certificate(s) without such legend if Columbia Bancorp
shall have delivered to Suburban Bancshares a copy of a letter from the staff of
the Securities and Exchange Commission, or an opinion of counsel, in form and
substance satisfactory to Suburban Bancshares, to the effect that such legend is
not required for purposes of the Securities Act of 1933, as amended (the
"Securities Act").

     5.  Representations.  Suburban Bancshares represents, warrants, and
covenants to Columbia Bancorp as follows:

          (a)  Suburban Bancshares shall at all times maintain sufficient
authorized but unissued shares of Suburban Bancshares Common Stock so that the
Option may be exercised without authorization of additional shares of Suburban
Bancshares Common Stock.

          (b)  The shares to be issued upon due exercise, in whole or in part,
of the Option, when paid for as provided herein, will be duly authorized,
validly issued, fully paid, and nonassessable.

     6.  Adjustment Upon Changes in Capitalization.  In the event of any change
in Suburban Bancshares Common Stock by reason of stock dividends, split-ups,
mergers, recapitalizations, combinations, exchanges of shares, or the like, the
type and number of shares subject to the Option, and the purchase price per
share, as the case may be, shall be adjusted appropriately.  In the event that
any additional shares of Suburban Bancshares Common Stock are issued or
otherwise become outstanding after the date of this Option Agreement (other than
pursuant to this Option Agreement), the number of shares of Suburban Bancshares
Common Stock subject to the Option shall be adjusted so that, after such
issuance, it equals 19.9% of the number of shares of Suburban Bancshares Common
Stock then issued and outstanding without giving effect to any shares subject or
issued pursuant to the Option.  Nothing contained in this Section 6 shall be
deemed to authorize Suburban Bancshares to breach any provision of the Plan.

     7.  Registration Rights.  If requested by Columbia Bancorp, Suburban
Bancshares shall as expeditiously as possible file a registration statement on a
form of general use under the Securities Act if necessary in order to permit the
sale or other disposition of the shares of Suburban Bancshares Common Stock that
have been acquired upon exercise of the Option in accordance with the intended
method of sale or other disposition requested by Columbia Bancorp.  Columbia
Bancorp shall provide all information reasonably requested by Suburban
Bancshares for inclusion in any registration statement to be filed hereunder.
Suburban Bancshares will use its best efforts to cause such registration
statement first to become effective and then to remain effective for such period
not in excess of 270 days from the day such registration statement first becomes
effective as may be reasonably necessary to effect such sales or other
dispositions.  Only one registration may be effected under this Section 7 at
Suburban Bancshares' expense, and which shall not include underwriting
commissions and the fees and disbursements of Columbia Bancorp's counsel
attributable to the registration of such Suburban Bancshares Common Stock.  The
filing of any registration statement hereunder may be delayed

                                      E-5
<PAGE>

for such period of time as may reasonably be required to facilitate any public
distribution by Suburban Bancshares of Suburban Bancshares Common Stock. If
requested by Columbia Bancorp, in connection with any such registration,
Suburban Bancshares will become a party to any underwriting agreement relating
to the sale of such shares, but only to the extent of obligating itself in
respect of representations, warranties, indemnities, and other agreements
customarily included in such underwriting agreements. Upon receiving any request
from Columbia Bancorp or assignee thereof under this Section 7, Suburban
Bancshares agrees to send a copy thereof to Columbia Bancorp and to any assignee
thereof known to Suburban Bancshares, in each case by promptly mailing the same,
postage prepaid, to the address of record of the persons entitled to receive
such copies.

     8.  Severability.  If any term, provision, covenant, or restriction
contained in this Option Agreement is held by a court or a federal or state
regulatory agency of competent jurisdiction to be invalid, void, or
unenforceable, the remainder of the terms, provisions, and covenants, and
restrictions contained in this Option Agreement shall remain in full force and
effect, and shall in no way be affected, impaired, or invalidated.  If for any
reason such court or regulatory agency determines that the Option will not
permit the holder to acquire the full number of shares of Suburban Bancshares
Common Stock provided in Section 2 (as adjusted pursuant to Section 6), it is
the express intention of Suburban Bancshares to allow the holder to acquire such
lesser number of shares as may be permissible, without any amendment or
modification hereof.

     9.  Miscellaneous.

          (a)  Expenses.  Except as otherwise provided herein, each of the
parties hereto shall bear and pay all costs and expenses incurred by it or on
its behalf in connection with the transactions contemplated hereunder, including
fees and expenses of its own financial consultants, investment bankers,
accountants, and counsel.

          (b)  Entire Agreement.  Except as otherwise expressly provided herein,
this Option Agreement contains the entire agreement between the parties with
respect to the transactions contemplated hereunder and supersedes all prior
arrangements or understandings with respect thereto, written or oral.  The terms
and conditions of this Option Agreement shall inure to the benefit of and be
binding upon the parties hereto and their respective successors and assigns.
Nothing in this Option Agreement, expressed or implied, is intended to confer
upon any party, other than the parties hereto, and their respective successors
and assigns, any rights, remedies, obligations or liabilities under or by reason
of this Option Agreement, except as expressly provided herein.

          (c)  Assignment.  Neither of the parties hereto may assign any of its
rights or obligations under this Option Agreement or the Option created
hereunder to any other person, without the express written consent of the other
party, except that in the event a Purchase Event shall have occurred and be
continuing Columbia Bancorp may assign in whole or in part its rights and
obligations hereunder; provided, however, that to the extent required by
applicable regulatory authorities, Columbia Bancorp may not assign its rights
under the Option except in (i)

                                      E-6
<PAGE>

a widely dispersed public distribution, (ii) a private placement in which no one
party acquires the right to purchase in excess of 2% of the voting shares of
Suburban Bancshares, (iii) an assignment to a single party (e.g., a broker or
investment banker) for the purpose of conducting a widely dispersed public
distribution on Columbia Bancorp's behalf, or (iv) any other manner approved by
applicable regulatory authorities.

          (d)  Notices.  All notices or other communications which are required
or permitted hereunder shall be in writing and sufficient if delivered in the
manner and to the address provided for in or pursuant to Section 15 of the Plan.

          (e)  Counterparts.  This Option Agreement may be executed in any
number of counterparts, and each such counterpart shall be deemed to be an
original instrument, but all such counterparts together shall constitute but one
agreement.

          (f)  Specific Performance.  The parties agree that damages would be an
inadequate remedy for a breach of the provisions of this Option Agreement by
either party hereto and that this Option Agreement may be enforced by either
party hereto through injunctive or other equitable relief.

          (g)  Governing Law.  This Option Agreement shall be governed by and
construed in accordance with the laws of the State of Maryland applicable to
agreements made and entirely to be performed within such state and such federal
laws as may be applicable.

                                      E-7
<PAGE>

     IN WITNESS WHEREOF, each of the parties hereto has executed this Option
Agreement as of the day and year first written above.


                              SUBURBAN BANCSHARES, INC.


                            By:________________________________________
                               Winfield M. Kelly, Jr.
                               Chairman of the Board
                               and Chief Executive Officer


                               COLUMBIA BANCORP


                            By:________________________________________
                               John M. Bond, Jr.
                               President and Chief Executive Officer

                                      E-8
<PAGE>

                                  APPENDIX F
                  OPINION OF AUSTIN FINANCIAL SERVICES, INC.


September 24, 1999


Board of Directors
Columbia Bancorp
10480 Little Patuxent Parkway
Columbia, Maryland 21044

Members of the Board:

     You have requested our opinion, from a financial point of view, as to the
fairness to Columbia Bancorp, ("Columbia") Columbia, Maryland and its
shareholders of the proposed terms of the Plan and Agreement to Merge
("Agreement"), between Suburban Bancshares, Inc., ("Suburban")
Greenbelt, Maryland and Columbia.  The reorganization will result in the merger
of Suburban with and into Columbia, the separate corporate existence of Suburban
shall cease, and Columbia shall continue as the successor corporation.  Columbia
will continue to carry on its banking business in substantially the same manner
as before the reorganization.

     Austin Financial Services, Inc., ("AFSI") is a nationally recognized
investment banking firm specializing in the banking and financial services
industry.  AFSI is continually engaged in the valuation of businesses and
securities in connection with mergers and acquisitions, private placements and
valuations for estate, corporate and other purposes.  In the past, AFSI has not
provided professional services and/or products to Columbia or Suburban in the
ordinary course of business.  Furthermore, AFSI does not contemplate any future
business with Columbia and/or Suburban arising from this engagement, nor has its
opinion concerning the fairness, from a financial point of view, of the terms of
the Agreement been subject to indications of future business with
either Columbia or Suburban.

     In connection with its opinion, AFSI reviewed material bearing upon the
financial operating condition of Columbia and Suburban including, but not
limited to: (1) the Annual Report of Suburban for the year ending 1998; (2)
Consolidated Reports of Condition and Income of Suburban for the years ending
1994-1998 and for June 30, 1999; (3) SEC form 10Q of Suburban for June 30, 1999;
(4) Uniform Bank Performance Report of Suburban for June 30, 1999; (5) the
investment security portfolio of Suburban as of August 31, 1999; (6) the
statement of financial condition of Suburban as of August 31, 1999; (7) rate
sensitivity analysis data of Suburban's loan portfolio as of August 31, 1999;
(8) the interest rate schedule for Suburban as of September 14, 1999; (9)
Suburban's stock price history from July 1, 1999 to September 16, 1999; (10) the
trial balance of Suburban as of August 31, 1999; (11) the classified assets and
watch loan list of Suburban as of August 31, 1999; (12) the nonaccrual loan list
of Suburban as of August 31, 1999; (13) depreciation projection for Suburban for
the years 2000-2004; (14) other internal financial and operating

                                      F-1
<PAGE>

information which was provided to AFSI by Suburban; (15) publicly available
information concerning certain other banks/thrifts and bank/thrift holding
companies, the trading markets for their securities and the nature and terms of
certain other merger and acquisition transactions believed relevant to its
inquiry; (16) the reported price and trading activity for Columbia's common
stock; (17) certain financial and stock market information for Columbia and
Suburban with similar information of certain other financial institutions whose
securities are publicly-traded; (18) discussed the foregoing as well as other
matters relevant to its inquiry, including the past and current business
operations and acquisitions, results of regulatory examinations, financial
condition, current loan quality and trends, and future prospects of Suburban
with certain officers and representatives of Suburban; and (19) the Agreement.
AFSI also took into account its assessment of general economic, market and
financial conditions and its experience in other transactions, as well as, its
experience in securities valuation and general knowledge of the banking
industry. AFSI's opinion was necessarily based upon conditions as they existed
and could be evaluated on the date of the opinion and the information made
available to AFSI through that date.

     AFSI relied upon and assumed without independent verification the accuracy
and completeness of all of the financial and other information provided to it by
Columbia and Suburban or from public sources.  AFSI has not made an independent
evaluation of the assets of Suburban, but has relied upon the books and records,
where applicable, of Suburban, and the audited financial statements as presented
to AFSI as the valuators of the fair market value of Suburban.  AFSI did not
independently verify and relied on and assumed the aggregate allowances for loan
losses set forth in the balance sheet for Suburban at August 31, 1999, were
adequate to cover such losses and complied fully with applicable law, regulatory
policy, and sound banking practice as of the date of such financial statements.
AFSI did not independently verify the carrying values of other real estate owned
and loans classified as in-substance foreclosures of Suburban in its respective
August 31, 1999, balance sheet, and AFSI assumed that such carrying values
complied fully with applicable law, regulatory policy and sound banking practice
as of such date.  AFSI did not make any independent evaluation or appraisal of
the assets, liabilities or prospects of Suburban, nor was AFSI furnished with
any such evaluation or appraisal. AFSI also assumed that the Agreement is, and
will be, in compliance with all laws and regulations that are applicable to
Columbia and Suburban.

     In its analyses, AFSI made numerous assumptions with respect to industry
performance, business and economic conditions, and other matters, many of which
are beyond the control of Columbia and Suburban.  Any estimates contained in
AFSI's analyses are not necessarily indicative of future results or value, which
may be significantly more or less favorable than such estimates.  AFSI's
estimates of values of other financial institutions used in its analyses do not
purport to be appraisals or necessarily reflect the price at which these
financial institutions or their securities actually may be sold.  No financial
institution or transaction utilized in AFSI's analyses was identical to Columbia
or Suburban or the Agreement. Accordingly, such analyses are not based solely on
arithmetic calculations; rather, they involve complex considerations and
judgments by AFSI concerning differences in financial and operating
characteristics of the relevant financial institutions, the timing of the
relevant transactions and prospective buyer interest, as well as other factors
that could affect the public trading markets of the financial institution or
financial institutions to which they are being compared.

     The following is a brief description of the analyses performed by AFSI in
connection with its opinion as described to Columbia's board of directors by
AFSI:

     Under the terms of the Agreement between Columbia and Suburban, each share
of Suburban common stock outstanding immediately prior to consummation of the
reorganization, will be cancelled and exchanged for

                                      F-2
<PAGE>

of Columbia common stock equivalent to an average market value of $3.00 per
share. The exchange ratio necessary to cause the average market value of shares
of Columbia common stock exchanged for each share of Suburban common stock to be
$3.00 per share will continually change until the merger is completed, except
that the exchange ratio will not be above .2338 nor decreased below .2196. The
reorganization will result in Suburban merging with and into Columbia, the
separate corporate existence of Suburban shall cease, and Columbia shall
continue as the successor corporation. Columbia will continue to carry on its
banking business in substantially the same manner as before the reorganization.

     Using a discounted cash flow analysis, AFSI projected Suburban's cash flow
from August 31, 2000, through August 31, 2004, assuming a minimum equity capital
to asset ratio of 6.00%.  AFSI also estimated the residual value of Suburban's
common equity as of August 31, 2004.  The steps involved in determining the
discounted cash flow value of Suburban included the following: (1) the projected
earnings in excess over the amount necessary to maintain a 6.00% equity capital
to asset ratio were added to book charges such as depreciation less any
projected capital expenditures in order to determine future cash flows; (2) the
future cash flows were then converted to a present value equivalent using a
discount rate of 17.20%, which was determined from the use of the Capital Asset
Pricing Model ("CAPM"); (3) the residual value was then calculated by dividing
the projected cash flows for the year 2004 by the capitalization rate.  The
capitalization rate not only includes all aspects of the CAPM but also reflects
the long-term income growth prospects of Suburban, as well as specific company
risk factors; (4) the present value equivalent of the projected residual value
was calculated using the 17.20% discount rate; and (5) the present value of the
cash flows and the residual value were added together.  The present value per
share currently outstanding of Suburban's common stock resulting from this
analysis was $3.21 (assuming 11,301,218 shares outstanding).

     AFSI also determined the adjusted book value of Suburban as an alternative
valuation method.  The adjusted book value approach requires a three-step
process.  First, the book value is determined.  This figure is derived from the
August 31, 1999, balance sheet, and it represents the summary measure of
stockholders' claims against the assets, on a historical cost basis.  Second,
assets and liabilities are restated to their fair market values.  The adjusted
book value calculation considers each major asset and liability account
classification.  Finally, additional "off-balance sheet" adjustments are
calculated, if necessary.  The fair market value per share currently outstanding
of Suburban's common stock resulting from this analysis was $2.71.

     AFSI applied a 75% weighting to the discounted cash flow value and a 25%
weighting to the adjusted book value. The weightings were based on AFSI's review
of the financial position, history and recent performance of Suburban. The sum
of the weighted values or $3.08 per share equates to the fair market value of
Suburban. Based on the terms of the Agreement, a closing price per share of
$13.0625 for Columbia's common stock as of September 23, 1999, would result in a
$3.00 per share value for Suburban's shareholders. Therefore, the exchange terms
of the Agreement would be favorable, from a financial standpoint, to Columbia
shareholders since the transaction would result in a positive margin of $0.08
per share in comparison to the fair market value of Suburban as determined by
AFSI.

     AFSI analyzed certain other mergers and acquisitions that have consummated
over the past eight months in Maryland as well as other nearby states (including
the states of Delaware, West Virginia, New Jersey, Pennsylvania, and Virginia)
involving target financial institutions with assets under $700 million. AFSI
compared the multiple produced by this reorganization to the mean multiples for
the transactions analyzed. Set forth below are the mean transaction multiples:

                                      F-3
<PAGE>

<TABLE>
<CAPTION>

                                    Selected
                                  Bank/Thrift
                                  Acquisitions  Suburban
                                  ------------  --------
<S>                               <C>           <C>
     Price/Earnings Multiple             27.73     28.61
     Price/Book Value Multiple          197.42    161.11
</TABLE>

     The financial institution acquisition transactions announced for the four-
state area during the past twelve months included in the above multiples are:

<TABLE>
<S>                                                  <C>
Buyer (City, State)                                  Target (City, State)
BB&T Corporation (Winston-Salem, NC)                 Matewan Bancshares Inc. (Williamson, WV)
CNB Financial Corporation (Clearfield, PA)           First National Bank of Spangler (Spangler, PA)
ESB Financial Corporation (Ellwood City, PA)         SHS Bancorp Inc. (Pittsburgh, PA)
F&M Bancorp (Frederick, MD)                          Patapsco Valley Bancshares Inc. (Ellicott City,
                                                     MD)
FCNB Corp. (Frederick, MD)                           First Frederick Financial Corp. (Frederick, MD)
First Leesport Bancorp Inc. (Leesport, PA)           Merchants of Shenandoah Ban-Corp (Shenandoah, PA)
FNB Financial Services Corporation (Reidsville, NC)  Black Diamond Savings Bank FSB (Norton, VA)
Hudson United Bancorp (Mahwah, NJ)                   Little Falls Bancorp Inc. (Little Falls, NJ)
Hudson United Bancorp (Mahwah, NJ)                   Southern Jersey Bancorp of Del. Inc. (Bridgeton,
                                                     NJ)
Independence Community Bank Corp. (Brooklyn, NY)     Broad National Bancorporation (Newark, NJ)
Independence Community Bank Corp. (Brooklyn, NY)     Statewide Financial Corporation (Jersey City, NJ)
James River Bankshares Inc. (Suffolk, VA)            State Bank of Remington (Remington, VA)
Lehman Brothers Holdings Inc. (New York, NY)         DSB Bancorp Inc. (Wilmington, DE)
NBT Bancorp Inc. (Norwich, NY)                       Lake Ariel Bancorp Inc. (Lake Ariel, PA)
Peapack-Gladstone Financial Corporation              Chatham Savings FSB (Chatham, NJ)
 (Gladstone, NJ)
PSB Bancorp Inc. (Philadelphia, PA)                  First Bank of Philadelphia (Philadelphia, PA)
South Branch Valley Bancorp Inc. (Moorefield, WV)*   Potomac Valley Bank (Petersburg, WV)*
Southern Financial Bancorp (Warrenton, VA)           Horizon Bank of Virginia (Merrifield, VA)
Staten Island Bancorp Inc. (Staten Island, NY)       First State Bancorp (Howell Township, NJ)
Sterling Financial Corp. (Lancaster, PA)             Northeast Bancorp Inc. (North East, MD)
Virginia Commonwealth Financial Corp. (Culpeper,     Caroline Savings Bank (Bowling Green, VA)
 VA)
</TABLE>

    AFSI's analysis showed that the implied valuations of Suburban, applying
the mean transaction multiples described above to Suburban's last twelve months
earnings per share and book value per share as of August 31, 1999, was $2.91 per
share and $3.67 per share, respectively.  The results produced in

                                      F-4
<PAGE>

this analysis do not purport to be indicative of actual values or expected
values of Suburban or shares of Suburban common stock.

     Columbia and AFSI have entered into an arrangement relating to the services
to be provided by AFSI in connection with the Agreement.  In regards to AFSI's
services in determining an opinion as to the fairness, from a financial point
of view, of the terms of the Agreement, the cost is a contractual $17,500 plus
out of pocket expenses.  In addition, Columbia also has agreed to indemnify
AFSI and its officers, directors, shareholders, employees and agents for all
of its time, expenses, and any liability incurred as a result of AFSI's
proposed engagement by means of legal action, administrative proceedings or
threat thereof, unless such action, pending or threat thereof is caused by
AFSI's own unlawful conduct, breach of duty or negligence during the course of
performing AFSI's services.

     AFSI, in rendering its opinion, has assumed that the transaction will be a
tax-free reorganization with no material adverse tax consequences to any of the
parties involved.  In addition, AFSI has assumed that in the course of obtaining
the necessary regulatory approvals for the transaction, no condition will be
imposed upon Columbia or Suburban that will have a materially adverse impact on
the contemplated benefits of the proposed transaction to Columbia and Suburban
and their shareholders.

     Based upon AFSI's analysis and subject to the qualifications described
herein, considering all circumstances known to us and based upon other matters
considered relevant, AFSI believes that as of the date of this letter, the terms
of the Agreement from a financial point of view are fair to Columbia and its
shareholders.

On behalf of Austin Financial Services, Inc.


/s/ D. V. Austin
- ------------------------------
Dr. Douglas V. Austin
President and CEO

                                      F-5
<PAGE>

                                  APPENDIX G

                     OPINION OF DANIELSON ASSOCIATES INC.

                                      G-1
<PAGE>

                                         September 28, 1999

Board of Directors
Suburban Bancshares, Inc.
7505 Greenway Center Drive
Greenbelt, Maryland 20770

Dear Members of the Board:

     Set forth herein is Danielson Associates Inc.'s ("Danielson Associates")
independent opinion as to the "fairness" of the offer by Columbia Bancorp
("Columbia") of Columbia, Maryland to acquire all of the outstanding common
stock of Suburban Bancshares, Inc. ("Suburban") of Greenbelt, Maryland through
an exchange of stock with a value at the time of the offer of about $34 million.
The "fair" sale value is defined as the price at which all of the shares of
Suburban Bancshares' common stock would change hands between a willing seller
and a willing buyer, each having reasonable knowledge of the relevant facts.  In
opining to the "fairness" of the offer, it also had to be determined if the
Columbia common stock to be exchanged for Suburban common stock was "fairly"
valued.

     In preparing the opinion, the markets served by Suburban have been
analyzed; its business and future prospects have been reviewed; its financial
performance has been compared with banks in the region; and the acquisition
prices of comparable banks have been analyzed.  In addition, any unique
characteristics have been considered.

     This opinion is based on data supplied by Suburban, and relies on some
public information, all of which is believed to be reliable, but the accuracy or
the completeness of such information cannot be guaranteed.  The opinion assumes
that there are no significant loan problems beyond what was stated in recent
reports to regulatory agencies.

     In determining the "fair" sale value of Suburban, the emphasis has been on
prices paid for banks and bank holding companies with similar financial,
structural and market characteristics.  These sale prices were then related to
earnings and equity capital, also referred to as "book."

     In determining the "fairness" of the offer, we compared the common stock to
be exchanged by Columbia for Suburban common stock with the common stock of
other, similar bank holding companies.  In so doing, we also compared Columbia's
financial performance with these comparable financial institutions.

     Based on the foregoing, we are of the opinion on the date hereof that the
offer made by Columbia to acquire all of the common stock of Suburban pursuant
to the merger agreement is "fair" from a financial point of view to Suburban and
its stockholders.


                                         Respectfully submitted,


                                         Jon D. Holtaway
                                         Senior Vice President

                                      G-2
<PAGE>

                                  APPENDIX H

                              SECTION 262 OF THE
                       DELAWARE GENERAL CORPORATION LAW

     (a)  Any stockholder of a corporation of this State who holds shares of
stock on the date of the making of a demand pursuant to subsection (d) of this
section with respect to such shares, who continuously holds such shares through
the effective date of the merger or consolidation, who has otherwise complied
with subsection (d) of this section and who has neither voted in favor of the
merger or consolidation nor consented thereto in writing pursuant to (S) 228 of
this title shall be entitled to an appraisal by the Court of Chancery of the
fair value of the stockholder's shares of stock under the circumstances
described in subsections (b) and (c) of this section.  As used in this section,
the word "stockholder" means a holder of record of stock in a stock corporation
and also a member of record of a nonstock corporation; the words "stock" and
"share" mean and include what is ordinarily meant by those words and also
membership or membership interest of a member of a nonstock corporation; and the
words "depository receipt" mean a receipt or other instrument issued by a
depository representing an interest in one or more shares, or fractions thereof,
solely of stock of a corporation, which stock is deposited with the depository.

     (b)  Appraisal rights shall be available for the shares of any class or
series of stock of a constituent corporation in a merger or consolidation to be
effected pursuant to (S) 251 (other than a merger effected pursuant to (S)
251(g) of this title), (S) 252, (S) 254, (S) 257, (S) 258, (S) 263 or (S) 264 of
this title:

               (1) Provided, however, that no appraisal rights under this shall
     be available for the shares of any class or series of stock, which stock,
     or depository receipts in respect thereof, at the record date fixed to
     determine the stockholders entitled to receive notice of and to vote at the
     meeting of stockholders to act upon the agreement of merger or
     consolidation, were either (i) listed on a national securities exchange or
     designated as a national market system security on an interdealer quotation
     system by the National Association of Securities Dealers, Inc. or (ii) held
     of record by more than 2,000 holders; and further provided that no
     appraisal rights shall be available for any shares of stock of the
     constituent corporation surviving a merger if the merger did not require
     for its approval the vote of the stockholders of the surviving corporation
     as provided in subsection (f) of (S) 251 of this title.

               (2) Notwithstanding paragraph (1) of this subsection, appraisal
     rights under this section shall be available for the shares of any class or
     series of stock of a constituent corporation if the holders thereof are
     required by the terms of an agreement of merger or consolidation pursuant
     to (S)(S) 251, 252, 254, 257, 258, 263 and 264 of this title to accept for
     such stock anything except:

                         a. Shares of stock of the corporation surviving or
               resulting from such merger or consolidation, or depository
               receipts in respect thereof;

                         b. Shares of stock of any other corporation, or
               depository receipts in respect thereof, which shares of stock (or
               depository receipts in respect thereof) or depository

                                      H-1
<PAGE>

               receipts at the effective date of the merger or consolidation
               will be either listed on a national securities exchange or
               designated as a national market system security on an interdealer
               quotation system by the National Association of Securities
               Dealers, Inc. or held of record by more than 2,000 holders;

                         c. Cash in lieu of fractional shares or fractional
               depository receipts described in the foregoing subparagraphs a.
               and b. of this paragraph; or

                         d. Any combination of the shares of stock, depository
               receipts and cash in lieu of fractional shares or fractional
               depository receipts described in the foregoing subparagraphs a.,
               b. and c. of this paragraph.

               (3) In the event all of the stock of a subsidiary Delaware
     corporation party to a merger effected under (S) 253 of this title is not
     owned by the parent corporation immediately prior to the merger, appraisal
     rights shall be available for the shares of the subsidiary Delaware
     corporation.

     (c)  Any corporation may provide in its certificate of incorporation that
appraisal rights under this section shall be available for the shares of any
class or series of its stock as a result of an amendment to its certificate of
incorporation, any merger or consolidation in which the corporation is a
constituent corporation or the sale of all or substantially all of the assets of
the corporation. If the certificate of incorporation contains such a provision,
the procedures of this section, including those set forth in subsections (d) and
(e) of this section, shall apply as nearly as is practicable.

     (d)  Appraisal rights shall be perfected as follows:

               (1) If a proposed merger or consolidation for which appraisal
     rights are provided under this section is to be submitted for approval at a
     meeting of stockholders, the corporation, not less than 20 days prior to
     the meeting, shall notify each of its stockholders who was such on the
     record date for such meeting with respect to shares for which appraisal
     rights are available pursuant to subsection (b) or (c) hereof that
     appraisal rights are available for any or all of the shares of the
     constituent corporations, and shall include in such notice a copy of this
     section. Each stockholder electing to demand the appraisal of such
     stockholder's shares shall deliver to the corporation, before the taking of
     the vote on the merger or consolidation, a written demand for appraisal of
     such stockholder's shares. Such demand will be sufficient if it reasonably
     informs the corporation of the identity of the stockholder and that the
     stockholder intends thereby to demand the appraisal of such stockholder's
     shares. A proxy or vote against the merger or consolidation shall not
     constitute such a demand. A stockholder electing to take such action must
     do so by a separate written demand as herein provided. Within 10 days after
     the effective date of such merger or consolidation, the surviving or
     resulting corporation shall notify each stockholder of each constituent
     corporation who has complied with this subsection and has not voted in
     favor of or consented to the merger or consolidation of the date that the
     merger or consolidation has become effective; or

               (2) If the merger or consolidation was approved pursuant to (S)
     228 or (S) 253 of this title, each constituent corporation, either before
     the effective date of the merger or consolidation or within ten days
     thereafter, shall notify each of the holders of any class or series of
     stock of such constituent corporation who are entitled to appraisal rights
     of the approval of the merger or

                                      H-2
<PAGE>

     consolidation and that appraisal rights are available for any or all shares
     of such class or series of stock of such constituent corporation, and shall
     include in such notice a copy of this section; provided that, if the notice
     is given on or after the effective date of the merger or consolidation,
     such notice shall be given by the surviving or resulting corporation to all
     such holders of any class or series of stock of a constituent corporation
     that are entitled to appraisal rights. Such notice may, and, if given on or
     after the effective date of the merger or consolidation, shall, also notify
     such stockholders of the effective date of the merger or consolidation. Any
     stockholder entitled to appraisal rights may, within 20 days after the date
     of mailing of such notice, demand in writing from the surviving or
     resulting corporation the appraisal of such holder's shares. Such demand
     will be sufficient if it reasonably informs the corporation of the identity
     of the stockholder and that the stockholder intends thereby to demand the
     appraisal of such holder's shares. If such notice did not notify
     stockholders of the effective date of the merger or consolidation, either
     (i) each such constituent corporation shall send a second notice before the
     effective date of the merger or consolidation notifying each of the holders
     of any class or series of stock of such constituent corporation that are
     entitled to appraisal rights of the effective date of the merger or
     consolidation or (ii) the surviving or resulting corporation shall send
     such a second notice to all such holders on or within 10 days after such
     effective date; provided, however, that if such second notice is sent more
     than 20 days following the sending of the first notice, such second notice
     need only be sent to each stockholder who is entitled to appraisal rights
     and who has demanded appraisal of such holder's shares in accordance with
     this subsection. An affidavit of the secretary or assistant secretary or of
     the transfer agent of the corporation that is required to give either
     notice that such notice has been given shall, in the absence of fraud, be
     prima facie evidence of the facts stated therein. For purposes of
     determining the stockholders entitled to receive either notice, each
     constituent corporation may fix, in advance, a record date that shall be
     not more than 10 days prior to the date the notice is given, provided, that
     if the notice is given on or after the effective date of the merger or
     consolidation, the record date shall be such effective date. If no record
     date is fixed and the notice is given prior to the effective date, the
     record date shall be the close of business on the day next preceding the
     day on which the notice is given.

     (e)  Within 120 days after the effective date of the merger or
consolidation, the surviving or resulting corporation or any stockholder who has
complied with subsections (a) and (d) hereof and who is otherwise entitled to
appraisal rights, may file a petition in the Court of Chancery demanding a
determination of the value of the stock of all such stockholders.
Notwithstanding the foregoing, at any time within 60 days after the effective
date of the merger or consolidation, any stockholder shall have the right to
withdraw such stockholder's demand for appraisal and to accept the terms offered
upon the merger or consolidation. Within 120 days after the effective date of
the merger or consolidation, any stockholder who has complied with the
requirements of subsections (a) and (d) hereof, upon written request, shall be
entitled to receive from the corporation surviving the merger or resulting from
the consolidation a statement setting forth the aggregate number of shares not
voted in favor of the merger or consolidation and with respect to which demands
for appraisal have been received and the aggregate number of holders of such
shares. Such written statement shall be mailed to the stockholder within 10 days
after such stockholder's written request for such a statement is received by the
surviving or resulting corporation or within 10 days after expiration of the
period for delivery of demands for appraisal under subsection (d) hereof,
whichever is later.

     (f)  Upon the filing of any such petition by a stockholder, service of a
copy thereof shall be made upon the surviving or resulting corporation, which
shall within 20 days after such service file in the office

                                      H-3
<PAGE>

of the Register in Chancery in which the petition was filed a duly verified list
containing the names and addresses of all stockholders who have demanded payment
for their shares and with whom agreements as to the value of their shares have
not been reached by the surviving or resulting corporation. If the petition
shall be filed by the surviving or resulting corporation, the petition shall be
accompanied by such a duly verified list. The Register in Chancery, if so
ordered by the Court, shall give notice of the time and place fixed for the
hearing of such petition by registered or certified mail to the surviving or
resulting corporation and to the stockholders shown on the list at the addresses
therein stated. Such notice shall also be given by 1 or more publications at
least 1 week before the day of the hearing, in a newspaper of general
circulation published in the City of Wilmington, Delaware or such publication as
the Court deems advisable. The forms of the notices by mail and by publication
shall be approved by the Court, and the costs thereof shall be borne by the
surviving or resulting corporation.

     (g)  At the hearing on such petition, the Court shall determine the
stockholders who have complied with this section and who have become entitled to
appraisal rights. The Court may require the stockholders who have demanded an
appraisal for their shares and who hold stock represented by certificates to
submit their certificates of stock to the Register in Chancery for notation
thereon of the pendency of the appraisal proceedings; and if any stockholder
fails to comply with such direction, the Court may dismiss the proceedings as to
such stockholder.

     (h)  After determining the stockholders entitled to an appraisal, the Court
shall appraise the shares, determining their fair value exclusive of any element
of value arising from the accomplishment or expectation of the merger or
consolidation, together with a fair rate of interest, if any, to be paid upon
the amount determined to be the fair value. In determining such fair value, the
Court shall take into account all relevant factors. In determining the fair rate
of interest, the Court may consider all relevant factors, including the rate of
interest which the surviving or resulting corporation would have had to pay to
borrow money during the pendency of the proceeding. Upon application by the
surviving or resulting corporation or by any stockholder entitled to participate
in the appraisal proceeding, the Court may, in its discretion, permit discovery
or other pretrial proceedings and may proceed to trial upon the appraisal prior
to the final determination of the stockholder entitled to an appraisal. Any
stockholder whose name appears on the list filed by the surviving or resulting
corporation pursuant to subsection (f) of this section and who has submitted
such stockholder's certificates of stock to the Register in Chancery, if such is
required, may participate fully in all proceedings until it is finally
determined that such stockholder is not entitled to appraisal rights under this
section.

     (i)  The Court shall direct the payment of the fair value of the shares,
together with interest, if any, by the surviving or resulting corporation to the
stockholders entitled thereto. Interest may be simple or compound, as the Court
may direct. Payment shall be so made to each such stockholder, in the case of
holders of uncertificated stock forthwith, and the case of holders of shares
represented by certificates upon the surrender to the corporation of the
certificates representing such stock. The Court's decree may be enforced as
other decrees in the Court of Chancery may be enforced, whether such surviving
or resulting corporation be a corporation of this State or of any state.

     (j)  The costs of the proceeding may be determined by the Court and taxed
upon the parties as the Court deems equitable in the circumstances. Upon
application of a stockholder, the Court may order all or a portion of the
expenses incurred by any stockholder in connection with the appraisal
proceeding, including, without limitation, reasonable attorney's fees and the
fees and expenses of experts, to be charged pro rata against the value of all
the shares entitled to an appraisal.

                                      H-4
<PAGE>

     (k)  From and after the effective date of the merger or consolidation, no
stockholder who has demanded  appraisal rights as provided in subsection (d) of
this section shall be entitled to vote such stock for any purpose or to receive
payment of dividends or other distributions on the stock (except dividends or
other distributions payable to stockholders of record at a date which is prior
to the effective date of the merger or consolidation); provided, however, that
if no petition for an appraisal shall be filed within the time provided in
subsection (e) of this section, or if such stockholder shall deliver to the
surviving or resulting corporation a written withdrawal of such stockholder's
demand for an appraisal and an acceptance of the merger or consolidation, either
within 60 days after the effective date of the merger or consolidation as
provided in subsection (e) of this section or thereafter with the written
approval of the corporation, then the right of such stockholder to an appraisal
shall cease. Notwithstanding the foregoing, no appraisal proceeding in the Court
of Chancery shall be dismissed as to any stockholder without the approval of the
Court, and such approval may be conditioned upon such terms as the Court deems
just.

     (l)  The shares of the surviving or resulting corporation to which the
shares of such objecting stockholders would have been converted had they
assented to the merger or consolidation shall have the status of authorized and
unissued shares of the surviving or resulting corporation.

                                      H-5
<PAGE>

                                    PART II

            INFORMATION NOT REQUIRED IN PROXY STATEMENT/PROSPECTUS


Item 20.  Indemnification of Directors and Officers.

     As permitted by the Maryland General Corporation Law ("MGCL"), Article
Eighth, Paragraph 5 of the Company's Charter provides for indemnification of
directors and officers of the Company, as follows:

          The Corporation shall indemnify (a) its directors to the
     full extent provided by the general laws of the State of Maryland
     now or hereafter in force, including the advance of expenses
     under the procedures provided by such laws; (b) its officers to
     the same extent it shall indemnify its directors; and (c) its
     officers who are not directors to such further extent as shall be
     authorized by the Board of Directors and be consistent with law.
     The foregoing shall not limit the authority of the Corporation to
     indemnify other employees and agents consistent with law.

     The Company's By-Laws contain indemnification procedures that implement
those of the Charter. The MGCL permits a corporation to indemnify its directors
and officers, among others, against judgments, penalties, fines, settlements and
reasonable expenses actually incurred by them in connection with any proceeding
to which they may be made a party by reason of their service in those or other
capacities, unless it is established that (a) the act or omission of the
director or officer was material to the matter giving rise to such proceeding
and (i) was committed in bad faith or (ii) was the result of active and
deliberate dishonesty, (b) the director or officer actually received an improper
personal benefit in money, property or services, or (c) in the case of any
criminal proceeding, the director or officer had reasonable cause to believe
that the action or omission was unlawful.

     As permitted by the MGCL, Article Eighth, Paragraph (6) of the Company's
Charter provides for limitation of liability of directors and officers of the
Company, as follows:

          To the fullest extent permitted by Maryland statutory or
     decisional law, as amended or interpreted, no director or officer
     of this Corporation shall be personally liable to the Corporation
     or its stockholders for money damages. No amendment of the
     charter of the Corporation or repeal of any of its provisions
     shall limit or eliminate the benefits provided to directors and
     officers under this provision with respect to any act or omission
     which occurred prior to such amendment or repeal.

     The MGCL permits the charter of a Maryland corporation to include a
provision limiting the liability of its directors and officers to the
corporation and its stockholders for money damages, except to the extent that
(i) the person actually received an improper benefit or profit in money,
property or services or (ii) a judgment or other final adjudication is entered
in a proceeding based on a finding that the person's action, or failure to act,
was the result of active and deliberate dishonesty and was material to the cause
of action adjudicated in the proceeding.
<PAGE>

       As permitted under Section 2-418(k) of the MGCL, the Company has
purchased and maintains insurance on behalf of its directors and officers
against any liability asserted against such directors and officers in their
capacities as such, whether or not the registrant would have the power to
indemnify such persons under the provisions of Maryland law governing
indemnification.

Item 21.  Exhibits and Financial Statements.

 2.1   Plan and Agreement to Merge, dated September 28, 1999, among Columbia
       Bancorp and Suburban Bancshares, Inc., previously filed with the
       Commission as an Exhibit to, and incorporated herein by reference from,
       the Form 8-K filed by Columbia Bancorp on October 4, 1999.

 2.2   First Amendment to Plan and Agreement to Merge, dated November 24, 1999,
       among Columbia Bancorp and Suburban Bancshares, Inc.

 3.1   Form of Restated Articles of Incorporation of Columbia Bancorp, restated
       as of December 31, 1995, previously filed with the Commission as an
       Exhibit to, and incorporated herein by reference from, the Annual Report
       on Form 10-KSB for fiscal year ended December 31, 1995
       (File No. 0-23402).

 3.2   Form of Amended and Restated By-Laws of Columbia Bancorp, restated as of
       September 27, 1999, previously filed with the Commission as an Exhibit
       to, and incorporated herein by reference from, the Form 8-K filed by
       Columbia Bancorp on October 4, 1999.

 5.1   Opinion of Piper Marbury Rudnick & Wolfe LLP re: legality *

 8.1   Opinion of Piper Marbury Rudnick & Wolfe LLP re: tax matters *

10.1   Form of the Company's 1987 Stock Option Plan, as amended April 17, 1990,
       December 18, 1995, and February 24, 1997, previously filed with the
       Commission as an Exhibit to, and incorporated herein by reference from,
       the Company's Annual Report on Form 10-K for fiscal year ended
       December 31, 1996 (File No. 0-23402).

10.1a  Amendment dated September 28, 1998 to the Company's 1987 Stock Option
       Plan filed as Exhibit to and incorporated herein by reference from, the
       Company's Annual Report on Form 10-K for fiscal year ended December 31,
       1998 (File No. 0-23402).

10.2   Form of Incentive Stock Option Agreement for use under the 1987 Stock
       Option Plan, as amended, previously filed with the Commission as an
       Exhibit to, and incorporated herein by reference from, the Company's
       Registration Statement on Form S-8 filed August 15, 1996
       (Reg. No. 333-10231).

10.3   Form of Non-Qualified Stock Option Agreement for use under the 1987 Stock
       Option Plan, as amended, previously filed with the Commission as an
       Exhibit to, and incorporated herein by reference from, the Company's
       Registration Statement on Form S-8 filed August 15, 1996
       (Reg. No. 333-10231).

10.4   Form of the Company's 1990 Director Stock Option Plan, as amended July
       29, 1996 and February 24, 1997, previously filed with the Commission as
       an Exhibit to, and incorporated herein by reference from, the Company's
       Annual Report on Form 10-K for fiscal year ended December 31, 1996
       (File No. 0-23402).

10.5   Form of Employment Agreement dated February 26, 1996 with John M. Bond,
       Jr., previously filed with the Commission as an Exhibit to, and
       incorporated herein by reference from, the Company's Annual Report on
       Form 10-KSB for fiscal year ended December 31, 1995 (File No. 0-23402).

10.5a  Amendment dated December 18, 1997 to the employment agreement dated
       February 26, 1996 with John M. Bond, Jr., previously filed with the
       Commission as an Exhibit to, and incorporated
<PAGE>

       herein by reference from, the Company's Annual Report on Form 10-K for
       fiscal year ended December 31, 1997 (File No.0-23402).

10.6   Form of Employment Agreement dated February 26, 1996 with Michael T.
       Galeone, previously filed with the Commission as an Exhibit to, and
       incorporated herein by reference from, the Company's Annual Report on
       Form 10-KSB for fiscal year ended December 31, 1995 (File No. 0-23402).

10.6a  Amendment dated December 16, 1997 to the employment agreement dated
       February 26, 1996 with Michael T. Galeone, previously filed with the
       Commission as an Exhibit to, and incorporated herein by reference from,
       the Company's Annual Report on Form 10-K for fiscal year ended
       December 31, 1997 (File No.0-23402).

10.7   Form of Employment Agreement dated February 27, 1996 with Charles C.
       Holman, previously filed with the Commission as an Exhibit to, and
       incorporated herein by reference from, the Company's Annual Report on
       Form 10-KSB for fiscal year ended December 31, 1995 (File No. 0-23402).

10.7a  Amendment dated December 16, 1997 to the employment agreement dated
       February 27, 1996 with Charles C. Holman, previously filed with the
       Commission as an Exhibit to, and incorporated herein by reference from,
       the Company's Annual Report on Form 10-K for fiscal year ended
       December 31, 1997 (File No .0-23402).

10.8   Form of Employment Agreement dated February 26, 1996 with John A.
       Scaldara, Jr., previously filed with the Commission as an Exhibit to, and
       incorporated herein by reference from, the Company's Annual Report on
       Form 10-KSB for fiscal year ended December 31, 1995 (File No. 0-23402).

10.8a  Amendment dated December 16, 1997 to the employment agreement dated
       February 26, 1996 with John A. Scaldara, Jr. previously filed with the
       Commission as an Exhibit to, and incorporated herein by reference from,
       the Company's Annual Report on Form 10-KSB for fiscal year ended
       December 31, 1997 (File No.0-23402).

10.9   Form of Employment Agreement dated February 26, 1999 with Robert W.
       Locke, previously filed with the Commission as an Exhibit to, and
       incorporated herein by reference from, the Company's Annual Report on
       Form 10-K for fiscal year ended December 31, 1998 (File No.0-23402).

10.10  Deferred Compensation Plan dated September 27, 1996, as amended December
       30, 1996, and February 24, 1997, including addendums thereto, previously
       filed with the Commission as an Exhibit to, and incorporated herein by
       reference from, the Company's Annual Report on Form 10-K for fiscal year
       ended December 31, 1996, (File No. 0-23402).

10.11  Data Processing agreements by and between the Bank and M&I Data Services,
       Inc., including addendums thereto, previously filed with the Commission
       as an Exhibit to, and incorporated herein by reference from, the
       Company's Annual Report on Form 10-K for fiscal year ended December 31,
       1996 (File No. 0-23402).

10.12  Form of the Company's 1997 Stock Option Plan, previously filed with the
       Commission as an Exhibit to, and incorporated herein by reference from,
       the Company's Registration Statement on Form S-8 filed July 29, 1997
       (Reg. No. 333-10231).

10.12a Amendment dated September 26, 1998 to the Company's 1997 Stock Option
       Plan previously filed with the Commission as an Exhibit to, and
       incorporated herein by reference from, the Company's Annual Report on
       Form 10-K for fiscal year ended December 31, 1998 (File No. 0-23402).

10.13  Form of Board Chairman's Services Agreement with Winfield M. Kelly, Jr.

10.14  Form of Employment Agreement with Stephen A. Horvath.
<PAGE>

10.15  Columbia Bancorp Stock Option Agreement with Suburban Bancshares, dated
       September 28, 1999. (included as Appendix D to the proxy
       statement/prospectus).

10.16  Suburban Bancshares Stock Option Agreement with Columbia Bancorp, dated
       September 28, 1999. (included as Appendix E to the proxy
       statement/prospectus).

10.17  Columbia Bancorp Support Agreement with Suburban Bancshares (included as
       Appendix B to the proxy statement/prospectus).

10.18  Suburban Bancshares Support Agreement with Columbia Bancorp (included as
       Appendix C to the proxy statement/prospectus).

13.1   Form 10-K for Columbia Bancorp for the year ended December 31, 1998,
       (Incorporated by reference to the Form 10-K filed by Columbia Bancorp on
       March 30, 1999)

13.2   Form 10-Q for Columbia Bancorp for the quarter ended September 30, 1999
       (Incorporated by reference to the Form 10-Q filed by Columbia Bancorp on
       November 15, 1999)
13.3   Form 10-K for Suburban Bancshares for the year ended December 31, 1998
       (Incorporated by reference to the Form 10-K filed by Suburban Bancshares
       on March 24, 1999)

13.4   Form 10-K/A for Suburban Bancshares for the year ended December 31, 1998
       (Incorporated by reference to the Form 10-K/A filed by Suburban
       Bancshares on April 27, 1999)

13.5   Form 10-Q for Suburban Bancshares, Inc. for the quarter ended September
       30, 1999 (Incorporated by reference to the Form 10-Q filed by Suburban
       Bancshares on November 5, 1999)

21.1   List of Subsidiaries of the Company, previously filed with the Commission
       as an Exhibit to, and incorporated herein by reference from, the
       Company's Annual Report on Form 10-K for fiscal year ended December 31,
       1998 (File No. 0-23402).

23.1   Consent of Stegman & Company

23.2   Consent of KPMG LLP

23.3   Consent of Piper Marbury Rudnick & Wolfe LLP (included in Exhibit 5.01
       and 8.01 hereto) *

23.4   Consent of Austin Financial Services, Inc.

23.5   Consent of Danielson Associates Inc.

24.1   Powers of Attorney

99.1   Form of proxy card for Columbia Bancorp stockholders *

99.2   Form of proxy card for Suburban Bancshares stockholders *

99.3   Opinion of Austin Financial Services, Inc. (included as Appendix F to the
       proxy statement/prospectus).

99.4   Opinion of Danielson Associates Inc. (included as Appendix G to the proxy
       statement/prospectus).
________________________
* To be filed by amendment.

Item 22.  Undertakings.

       The undersigned registrant hereby undertakes:

       (1) To file, during any period in which offers and sales are being made,
a post-effective amendment to this registration statement:

           (i) To include any prospectus required by Section 10(a)(3) of the
       Securities Act of 1933;
<PAGE>

           (ii) To reflect in the prospectus any facts or events arising after
       the effective date of the registration statement (or the most recent
       post-effective amendment thereof) which, individually or in the
       aggregate, represent a fundamental change in the information set forth in
       the registration statement. Notwithstanding the foregoing, any increase
       or decrease in volume of securities offered (if the total dollar value of
       securities offered would not exceed that which was registered) and any
       deviation from the low or high end of the estimated maximum offering
       range may be reflected in the form of prospectus filed with the
       Commission pursuant to Rule 424(b) if, in the aggregate, the changes in
       volume and price represent no more than a 20% change in the maximum
       aggregate offering price set forth in the "Calculation of Registration
       Fee" table in the effective registration statement; and

           (iii) To include any material information with respect to the plan of
       distribution not previously disclosed in the registration statement or
       any material change to such information in the registration statement.

       Provided, however, that paragraphs (1)(i) and (1)(ii) do not apply if the
       information required to be included in a post-effective amendment by
       those paragraphs is contained in periodic reports filed with or furnished
       to the Commission by the registrant pursuant to Section 13 or 15(d) of
       the Securities Exchange Act of 1934 that are incorporated by reference in
       the registration statement.

       (2) That, for the purpose of determining any liability under the
Securities Act of 1933, each such post-effective amendment shall be deemed to be
a new registration statement relating to the securities offered therein, and the
offering of such securities at that time shall be deemed to be the initial bona
fide offering thereof.

       (3) To remove from registration by means of a post-effective amendment
any of the securities being registered which remain unsold at the termination of
the offering.

       The undersigned registrant hereby undertakes that, for purposes of
determining any liability under the Securities Act of 1933, each filing of the
registrant's annual report pursuant to Section 13(a) or Section 15(d) of the
Securities Exchange Act of 1934 that is incorporated by reference in the
registration statement shall be deemed to be a new registration statement
relating to the securities offered therein, and the offering of such securities
at that time shall be deemed to be the initial bona fide offering thereof.

       The undersigned registrant hereby undertakes as follows: that prior to
any public reoffering of the securities registered hereunder through use of a
prospectus which is a part of this registration statement, by any person or
party who is deemed to be an underwriter within the meaning of Rule 145(c), the
issuer undertakes that such reoffering prospectus will contain the information
called for by the applicable registration form with respect to reofferings by
persons who may be deemed underwriters, in addition to the information called
for by the other items of the applicable form.

       The registrant undertakes that every prospectus: (1) that is filed
pursuant to paragraph (1) immediately preceding, or (ii) that purports to meet
the requirements of Section 10(a)(3) of the Securities Act of 1933 and is used
in connection with an offering of securities subject to Rule 415, will be filed
as a part of an amendment to the registration statement and will not be used
until such amendment is effective, and that, for purposes of determining any
liability under the Securities Act of 1933, each such post-effective amendment
shall be deemed to be a new registration statement relating to the securities
offered
<PAGE>

therein, and the offering of such securities at that time shall be deemed to be
the initial bona fide offering thereof.

     Insofar as indemnification for liabilities arising under the Securities Act
of 1933 may be permitted to directors, officers and controlling persons of the
registrant pursuant to the foregoing provisions, or otherwise, the registrant
has been advised that in the opinion of the Securities and Exchange Commission
such indemnification is against public policy as expressed in the Act and is,
therefore, unenforceable. In the event that a claim for indemnification against
such liabilities (other than the payment by the registrant of expenses incurred
or paid by a director, officer or controlling person of the registrant in the
successful defense of any action, suit or proceeding) is asserted by such
director, officer or controlling person in connection with the securities being
registered, the registrant will, unless in the opinion of its counsel the matter
has been settled by controlling precedent, submit to a court of appropriate
jurisdiction the question whether such indemnification by it is against public
policy as expressed in the Act and will be governed by the final adjudication of
such issue.

     The undersigned registrant hereby undertakes to respond to requests for
information that is incorporated by reference into the prospectus pursuant to
Items 4, 10(b), 11 or 13 of this Form, within one business day of receipt of
such request, and to send the incorporated documents by first-class mail or
other equally prompt means. This includes information contained in documents
filed subsequent to the effective date of the registration statement through the
date of responding to the request.

     The undersigned registrant hereby undertakes to supply by means of a post-
effective amendment all information concerning a transaction, and the company
being acquired involved therein, that was not the subject of and included in the
registration statement when it became effective.
<PAGE>

                                   SIGNATURES

     Pursuant to the requirements of the Securities Act, the registrant has duly
caused the registration statement to be signed on its behalf by the undersigned,
thereunto duly authorized in the city of Columbia, State of Maryland, on
November 23, 1999.

                                    Columbia Bancorp, Inc.



                                    By: /s/ James R. Moxley, Jr.
                                       -------------------------
                                       James R. Moxley, Jr.
                                       Chairman of the Board

     Pursuant to the requirements of the Securities Act of 1933, this
registration statement has been signed by the following persons in the
capacities on the dates indicated.


<TABLE>
<CAPTION>
         Signature                                  Title                                  Date
         ---------                                  -----                                  ----
<S>                           <C>                                               <C>
/s/ James R. Moxley, Jr.      Chairman of the Board                             November 23, 1999
- ----------------------------
James R. Moxley, Jr.

/s/ John M. Bond, Jr.         President and Chief Executive Officer             November 23, 1999
- ----------------------------  (Principal Executive Officer)
John M. Bond, Jr.

/s/ John A. Scaldara, Jr.     Executive Vice President, Finance and             November 23, 1999
- ----------------------------  Administration and Chief Financial Officer
John A. Scaldara, Jr.         (Principal Financial and Accounting Officer)

/s/ Herschel L. Langenthal    Director                                          November 23, 1999
- ----------------------------
Herschel L. Langenthal

                              Director                                          November 23, 1999
- ----------------------------
Anand S. Bhasin

/s/ Gannett Y. Clark, Jr.     Director                                          November 23, 1999
- ----------------------------
Gannett Y. Clark, Jr.

/s/ Hugh F.Z. Cole, Jr.       Director                                          November 23, 1999
- ----------------------------
Hugh F.Z. Cole, Jr.

                              Director                                          November 23, 1999
- ----------------------------
G. William Floyd

/s/ William L. Hermann        Director                                          November 23, 1999
- ----------------------------
William L. Herman
</TABLE>
<PAGE>

<TABLE>
<S>                           <C>                                               <C>
/s/ Charles C. Holman         Director                                          November 23, 1999
- ----------------------------
Charles C. Holman

/s/ Harry L. Lundy, Jr.       Director                                          November 23, 1999
- ----------------------------
Harry L. Lundy, Jr.

/s/ Richard E. McCready       Director                                          November 23, 1999
- ----------------------------
Richard E. McCready

/s/ James R. Moxley III       Director                                          November 23, 1999
- ----------------------------
James R. Moxley III

/s/ Mary S. Scrivener         Director                                          November 23, 1999
- ----------------------------
Mary S. Scrivener

/s/ Maurice M. Simpkins       Director                                          November 23, 1999
- ----------------------------
Maurice M. Simpkins

/s/ Robert N. Smelkinson      Director                                          November 23, 1999
- ----------------------------
Robert N. Smelkinson

/s/ Theodore G. Venetoulis    Director                                          November 23, 1999
- ----------------------------
Theodore G. Venetoulis
</TABLE>
<PAGE>

                                 EXHIBIT INDEX

 2.1  Plan and Agreement to Merge, dated September 28, 1999, among Columbia
      Bancorp and Suburban Bancshares, Inc., previously filed with the
      Commission as an Exhibit to, and incorporated herein by reference from,
      the Form 8-K filed by Columbia Bancorp on October 4, 1999.

 2.2  First Amendment to Plan and Agreement to Merge, dated November 24, 1999,
      among Columbia Bancorp and Suburban Bancshares, Inc.

 3.1  Form of Restated Articles of Incorporation of Columbia Bancorp, restated
      as of December 31, 1995, previously filed with the Commission as an
      Exhibit to, and incorporated herein by reference from, the Annual Report
      on Form 10-KSB for fiscal year ended December 31, 1995 (File No. 0-23402).

 3.2  Form of Amended and Restated By-Laws of Columbia Bancorp, restated as of
      September 27, 1999, previously filed with the Commission as an Exhibit to,
      and incorporated herein by reference from, the Form 8-K filed by Columbia
      Bancorp on October 4, 1999.

 5.1  Opinion of Piper Marbury Rudnick & Wolfe LLP re: legality *

 8.1  Opinion of Piper Marbury Rudnick & Wolfe LLP re: tax matters *

10.1  Form of the Company's 1987 Stock Option Plan, as amended April 17, 1990,
      December 18, 1995, and February 24, 1997, previously filed with the
      Commission as an Exhibit to, and incorporated herein by reference from,
      the Company's Annual Report on Form 10-K for fiscal year ended December
      31, 1996 (File No. 0-23402).

10.1a Amendment dated September 28, 1998 to the Company's 1987 Stock Option Plan
      filed as Exhibit to and incorporated herein by reference from, the
      Company's Annual Report on Form 10-K for fiscal year ended December 31,
      1998 (File No. 0-23402)

10.2  Form of Incentive Stock Option Agreement for use under the 1987 Stock
      Option Plan, as amended, previously filed with the Commission as an
      Exhibit to, and incorporated herein by reference from, the Company's
      Registration Statement on Form S-8 filed August 15, 1996 (Reg. No. 333-
      10231)

10.3  Form of Non-Qualified Stock Option Agreement for use under the 1987 Stock
      Option Plan, as amended (previously filed with the Commission as an
      Exhibit to, and incorporated herein by reference from, the Company's
      Registration Statement on Form S-8 filed August 15, 1996) (Reg. No. 333-
      10231).

10.4  Form of the Company's 1990 Director Stock Option Plan, as amended July 29,
      1996 and February 24, 1997, previously filed with the Commission as an
      Exhibit to, and incorporated herein by reference from, the Company's
      Annual Report on Form 10-K for fiscal year ended December 31, 1996 (File
      No. 0-23402).

<PAGE>

10.5  Form of Employment Agreement dated February 26, 1996 with John M. Bond,
      Jr., previously filed with the Commission as an Exhibit to, and
      incorporated herein by reference from, the Company's Annual Report on Form
      10-KSB for fiscal year ended December 31, 1995 (File No. 0-23402).

10.5a Amendment dated December 18, 1997 to the employment agreement dated
      February 26, 1996 with John M. Bond, Jr., previously filed with the
      Commission as an Exhibit to, and incorporated herein by reference from,
      the Company's Annual Report on Form 10-K for fiscal year ended December
      31, 1997 (File No.0-23402).

10.6  Form of Employment Agreement dated February 26, 1996 with Michael T.
      Galeone, previously filed with the Commission as an Exhibit to, and
      incorporated herein by reference from, the Company's Annual Report on Form
      10-KSB for fiscal year ended December 31, 1995 (File No. 0-23402).

10.6a Amendment dated December 16, 1997 to the employment agreement dated
      February 26, 1996 with Michael T. Galeone, previously filed with the
      Commission as an Exhibit to, and incorporated herein by reference from,
      the Company's Annual Report on Form 10-K for fiscal year ended December
      31, 1997 (File No.0-23402).

10.7  Form of Employment Agreement dated February 27, 1996 with Charles C.
      Holman, previously filed with the Commission as an Exhibit to, and
      incorporated herein by reference from, the Company's Annual Report on Form
      10-KSB for fiscal year ended December 31, 1995 (File No. 0-23402).

10.7a Amendment dated December 16, 1997 to the employment agreement dated
      February 27, 1996 with Charles C. Holman, previously filed with the
      Commission as an Exhibit to, and incorporated herein by reference from,
      the Company's Annual Report on Form 10-K for fiscal year ended December
      31, 1997 (File No .0-23402).

10.8  Form of Employment Agreement dated February 26, 1996 with John A.
      Scaldara, Jr., previously filed with the Commission as an Exhibit to, and
      incorporated herein by reference from, the Company's Annual Report on Form
      10-KSB for fiscal year ended December 31, 1995 (File No. 0-23402).

10.8a Amendment dated December 16, 1997 to the employment agreement dated
      February 26, 1996 with John A. Scaldara, Jr. previously filed with the
      Commission as an Exhibit to, and incorporated herein by reference from,
      the Company's Annual Report on Form 10-KSB for fiscal year ended December
      31, 1997 (File No.0-23402).

10.9  Form of Employment Agreement dated February 26, 1999 with Robert W. Locke,
      previously filed with the Commission as an Exhibit to, and incorporated
      herein by reference from, the Company's Annual Report on Form 10-K for
      fiscal year ended December 31, 1998 (File No.0-23402).

10.10 Deferred Compensation Plan dated September 27, 1996, as amended December
      30, 1996, and February 24, 1997, including addendums thereto, previously
      filed with the Commission as an
<PAGE>

       Exhibit to, and incorporated herein by reference from, the Company's
       Annual Report on Form 10-K for fiscal year ended December 31, 1996, (File
       No. 0-23402).

10.11  Data Processing agreements by and between the Bank and M&I Data Services,
       Inc., including addendums thereto, previously filed with the Commission
       as an Exhibit to, and incorporated herein by reference from, the
       Company's Annual Report on Form 10-K for fiscal year ended December 31,
       1996 (File No. 0-23402).

10.12  Form of the Company's 1997 Stock Option Plan, previously filed with the
       Commission as an Exhibit to, and incorporated herein by reference from,
       the Company's Registration Statement on Form S-8 filed July 29, 1997
       (Reg. No. 333-10231).

10.12a Amendment dated September 26, 1998 to the Company's 1997 Stock Option
       Plan previously filed with the Commission as an Exhibit to, and
       incorporated herein by reference from, the Company's Annual Report on
       Form 10-K for fiscal year ended December 31, 1998 (File No. 0-23402).

10.13  Form of Board Chairman's Services Agreement with Winfield M. Kelly, Jr..

10.14  Form of Employment Agreement with Stephen A. Horvath.

10.15  Columbia Bancorp Stock Option Agreement with Suburban Bancshares, dated
       September 28, 1999. (included as Appendix D to the proxy
       statement/prospectus).

10.16  Suburban Bancshares Stock Option Agreement with Columbia Bancorp, dated
       September 28, 1999. (included as Appendix E to the proxy
       statement/prospectus).

10.17  Columbia Bancorp Support Agreement with Suburban Bancshares (included as
       Appendix B to the proxy statement/prospectus).

10.18  Suburban Bancshares Support Agreement with Columbia Bancorp (included as
       Appendix C to the proxy statement/prospectus).

13.1   Form 10-K for Columbia Bancorp for the year ended December 31, 1998,
       (Incorporated by reference to the Form 10-K filed by Columbia Bancorp on
       March 30, 1999)

13.2   Form 10-Q for Columbia Bancorp for the quarter ended September 30, 1999
       (Incorporated by reference to the Form 10-Q filed by Columbia Bancorp on
       November 15, 1999)

13.3   Form 10-K for Suburban Bancshares for the year ended December 31, 1998
       (Incorporated by reference to the Form 10-K filed by Suburban Bancshares
       on March 24, 1999)

13.4   Form 10-K/A for Suburban Bancshares for the year ended December 31, 1998
       (Incorporated by reference to the Form 10-K/A filed by Suburban
       Bancshares on April 27, 1999)
<PAGE>

13.5   Form 10-Q for Suburban Bancshares, Inc. for the quarter ended September
       30, 1999 (Incorporated by reference to the Form 10-Q filed by Suburban
       Bancshares on November 5, 1999)

21.1   List of Subsidiaries of the Company, previously filed with the Commission
       as an Exhibit to, and incorporated herein by reference from, the
       Company's Annual Report on Form 10-K for fiscal year ended December 31,
       1998 (File No. 0-23402).

23.1   Consent of Stegman & Company

23.2   Consent of KPMG LLP

23.3   Consent of Piper Marbury Rudnick & Wolfe LLP (included in Exhibit 5.01
       and 8.01 hereto) *

23.4   Consent of Austin Financial Services, Inc.

23.5   Consent of Danielson Associates Inc.

24.1   Powers of Attorney

99.1   Form of proxy card for Columbia Bancorp stockholders *

99.2   Form of proxy card for Suburban Bancshares stockholders *

99.3   Opinion of Austin Financial Services, Inc. (included as Appendix F to the
       proxy statement/prospectus).

99.4   Opinion of Danielson Associates Inc. (included as Appendix G to the proxy
       statement/prospectus).

________________________
* To be filed by amendment.

<PAGE>

                                                                     EXHIBIT 2.2

                FIRST AMENDMENT TO PLAN AND AGREEMENT TO MERGE

     First Amendment to PLAN AND AGREEMENT TO MERGE (this "Amendment") dated as
of November __, 1999 to the PLAN AND AGREEMENT TO MERGE (the "Plan"), dated as
of September 28, 1999 by and between COLUMBIA BANCORP ("Columbia Bancorp"), a
Maryland corporation, and SUBURBAN BANCSHARES, INC. ("Suburban Bancshares"), a
Delaware corporation.

                             W I T N E S S E T H:

     WHEREAS, Columbia Bancorp and Suburban Bancshares are parties to the Plan
whereby Suburban Bancshares has agreed to merge with and into Columbia Bancorp,
with Columbia Bancorp as the surviving entity.

     WHEREAS, Suburban Bancshares and Columbia Bancorp wish to amend the Plan
pursuant to Section 12 of the Plan in order to provide for any stockholders of
Suburban Bancshares which exercise dissenters' rights of appraisal.

     NOW, THEREFORE, in consideration of the mutual covenants and agreements
herein contained and the mutual benefits to be derived herefrom, the parties
agree as follows:

     1.   Section 9.2 of the Plan is hereby amended by deleting that section in
its entirety and inserting the following in lieu thereof:

          9.2. Conversion of Stock; Conversion Ratio.  (a) On the Effective
     Date, each share of the Suburban Bancshares Common Stock outstanding
     immediately prior to the Effective Date (other than shares (the
     "Dissenters' Shares") with respect to which dissenter's rights shall have
     been perfected in accordance with De. General Corporation Law (S) 262),
     shall, without any action on the part of the holder thereof, be canceled
     and converted into the number of shares of Successor Corporation Common
     Stock (rounded to the nearest 0.01 share) which results after
     multiplication by the Conversion Ratio.  The Conversion Ratio shall be
     0.2196; provided, however, that the Conversion Ratio shall be increased
     (but not decreased) to the extent necessary to cause the average market
     value (based on the mean of the daily high and low trade prices, or, if
     none, of the daily high bid and low asked prices, reported on NASDAQ) of
     Columbia Bancorp Common Stock (for each of the 10 trading days ending on
     the trading date that is three days before the Effective Date) received for
     each share of Suburban Bancshares Common Stock to be $3.00 per share;
     provided, further that such adjustment may not increase the Conversion
     Ratio above 0.2338.

               (b)  No certificates for fractional shares of Successor
     Corporation Common Stock shall be issued; in lieu thereof, each holder
     otherwise entitled to a fractional interest shall receive an amount in cash
     based on the market value of Columbia Bancorp Common Stock as determined in
     Section 9.2. Each such holder shall have no other rights with respect to
     such fractional interest.

                                      -1-
<PAGE>

               (c)  Dissenters' Shares shall be paid for in accordance with De.
     General Corporation Law (S) 262 and thereupon shall be cancelled, retired
     and cease to exist.

               (d)  Notwithstanding any provision of this Plan to the contrary,
     any Dissenters' Shares, which as of the Effective Date the holder thereof
     has not withdrawn or lost any right to such appraisal shall not be
     exchanged, or represent a right to receive shares of Columbia Bancorp
     Common Stock, but the holder shall only be entitled to such rights as are
     granted by De. General Corporation Law (S) 262. If a stockholder of
     Suburban Bancshares who demands appraisal of his shares under De. General
     Corporation Law (S) 262 shall effectively withdraw or lose (through failure
     to perfect or otherwise) the right to appraisal, then, as of the Effective
     Date or the occurrence of such event, whichever last occurs, that
     stockholder's shares of the Suburban Bancshares Common Stock shall be
     exchanged and represent only the right to receive shares of Columbia
     Bancorp Common Stock as provided in Section 9.2(a) pursuant to the
     procedures in Section 9.3. Suburban Bancshares shall give Columbia Bancorp
     (a) prompt written notice of any written demands for appraisal of any share
     of the Suburban Bancshares Common Stock, attempted withdrawals of such
     demands and any other instruments served pursuant to the De. General
     Corporation Law (S) 262 relating to the Suburban Bancshares stockholders'
     rights of appraisal and (b) the opportunity to direct all negotiations and
     proceedings with respect to demands for appraisal under De. General
     Corporation Law (S) 262. Suburban Bancshares shall not, except with the
     prior written consent of Columbia Bancorp, voluntarily make any payment
     with respect to any demands for appraisals of share of the Suburban
     Bancshares Common Stock, offer to settle or settle any such demands or
     approve any withdrawal of any such demands. Notwithstanding any provision
     of this Plan to the contrary, Columbia Bancorp shall have the right to
     terminate this Plan and be released from all obligations hereunder if,
     immediately prior to the proposed Effective Date, Suburban Bancshares
     stockholders have demanded appraisal rights (which demands theretofore have
     not been withdrawn) in such numbers that jeopardize the accounting
     treatment specified in Section 7.10 and, KPMG LLP fails or refuses to
     deliver a letter to Columbia Bancorp to the effect that the Mergers qualify
     for pooling-of-interests accounting treatment, as provided in Section 7.10.

     2.   Section 13(d) of the Plan is hereby amended by deleting that
subsection in its entirety and inserting the following in lieu thereof:

               (d)  by Columbia Bancorp by written notice to Suburban Bancshares
     if prior to June 30, 2000 (i) any approval, consent, or waiver of any
     Governmental Entity required to permit consummation of the transactions
     contemplated hereby shall have been denied, (ii) any approval, consent, or
     waiver of any Governmental Entity required to permit consummation of the
     transactions contemplated hereby shall include any condition or requirement
     that would (i) result in a materially adverse effect on Columbia Bancorp or
     Suburban Bancshares, or (ii) so materially and adversely affect the
     economic or business benefits of the Mergers that Columbia Bancorp, in the
     sole judgment of Columbia

                                      -2-
<PAGE>

     Bancorp, would not have entered into this Plan had such conditions or
     requirements been known at the date hereof, (iii) any action or proceeding
     against Columbia Bancorp or any of the Columbia Subsidiaries or against
     Suburban Bancshares or any of the Suburban Subsidiaries shall be pending
     which seeks to prevent consummation of the transactions contemplated by
     this Plan, (iv) any court shall have entered an order which prohibits
     consummation of the Mergers and the transactions contemplated by this Plan,
     or (v) termination is permitted as provided in Section 9.2(d);

     3.   The Plan and all provisions thereof remain in full force and effect
unless specifically modified or amended hereby.

     IN WITNESS WHEREOF, Columbia Bancorp and Suburban Bancshares have caused
this Amendment to be duly executed by their respective chairmen or presidents,
and their respective seals to be hereunto affixed and attested by their
respective secretaries, thereunto duly authorized as of the date first above
written.

ATTEST:   [SEAL]                    COLUMBIA BANCORP

                                    By: ________________________________________
John A. Scaldara, Jr.                   John M. Bond, Jr.
Secretary                               President and Chief Executive Officer

ATTEST:   [SEAL]                    SUBURBAN BANCSHARES, INC.

                                    By: ________________________________________
                                        Winfield M. Kelly, Jr.
Secretary                               Chairman of the Board
                                        and Chief Executive Officer

                                      -3-

<PAGE>

                                                                   Exhibit 10.13

                      BOARD CHAIRMAN'S SERVICES AGREEMENT

     THIS SERVICE AGREEMENT (hereinafter this "Agreement") is entered into on
this ____ day of ____________________, by and between:

     (1)  Winfield M. Kelly, Jr.
          12404 Pleasant Prospect Road
          Mitchellville, Maryland 20721

(hereinafter "Kelly") and

     (2)  Columbia Bancorp
          9171 Baltimore National Pike
          Ellicott City, Maryland  21042

(hereinafter "Columbia Bancorp"), and its subsidiary, The Columbia Bank
(hereinafter "Columbia Bank").

                             W I T N E S S E T H:

     WHEREAS, Columbia Bancorp desires to provide to Kelly and Kelly desires to
receive from Columbia Bancorp a continuing services agreement so as to retain
and secure Kelly's services as Chairman of the Board of Directors of Columbia
Bancorp and Chairman of the Board of Directors of Columbia Bank, upon the terms
and conditions set forth in this Agreement.

     NOW THEREFORE, the parties, intending to be legally bound, agree as
follows:

     1.   Definitions.  As used in this Agreement, the following terms have the
          -----------
meanings set forth below:

             (a) Commencement Date.  _________________.
                 -----------------

             (b) Bank Regulatory Agency.  As used in this Agreement, "Bank
                 ----------------------
Regulatory Agency" shall mean any governmental authority, regulatory agency,
ministry, department, statutory corporation, central bank or other body of the
United States or of any other country or of any state or other political
subdivision of any of them having jurisdiction over Columbia Bancorp or any
transaction contemplated, undertaken or proposed to be undertaken by Columbia
Bancorp hereunder or otherwise.  Bank Regulatory Agency shall include, but not
necessarily be limited to:

                    (1) The Federal Deposit Insurance Corporation or any other
     federal or state depository insurance organization or fund; and

                    (2) The Federal Reserve System, the Comptroller of the
     Currency, The Maryland Division of Financial Regulation, or any other
     federal or state bank regulatory or commissioner's office; and
<PAGE>

              (3) The Resolution Trust Corporation, the Resolution Funding
     Corporation, the Financing Corporation or any other entity created pursuant
     to The Financial Institutions Reform, Recovery and Enforcement Act of 1989,
     as amended from time to time; and

              (4) Any corporation, bridge bank, fund association, or other
     entity established, organized, owned (in whole or in part) or controlled by
     any of the foregoing; and

              (5) Any predecessor, successor or assignee of the foregoing.

     2. Term.
        ----

          (a) Initial Term. Except as provided for below under "Rights to
              ------------
Terminate Agreement", the Initial Term of this Agreement shall expire upon the
expiration of Kelly's current term as a director of Columbia Bancorp.

               (1) Renewals and Extensions; Subsequent Annual Terms.  After the
                   ------------------------------------------------
     Initial Term of this Agreement, this Agreement shall automatically renew
     with the reelection of Kelly as BOARD CHAIRMAN in accordance with Columbia
     Bancorp's and Columbia Bank's By-Laws and Charter, unless:

                    (A) Kelly provides notice to Columbia Bancorp and Columbia
               Bank at least on or before the end of any term that he does not
               wish to renew the contract for an additional annual term, in
               which event this Agreement will expire at the end of the contract
               term in which Kelly gives such notice to Columbia Bancorp and
               Columbia Bank; or

                    (B) Kelly fails to be reelected as BOARD CHAIRMAN in
               accordance with Columbia Bancorp's and Columbia Bank's By-Laws
               and Charter.

     3.   Duties and Authority of Kelly.
          -----------------------------

               (a) Performance of Services. Kelly shall discharge his duties as
                   -----------------------
Board Chairman to the best of his ability for and on behalf of Columbia Bancorp
and Columbia Bank. Kelly shall comply with all laws, statutes, ordinances, rules
and regulations relating to his services and duties. During the term of this
Agreement, Kelly shall not at any time or place directly or indirectly engage or
agree to engage in any business or practice related to the banking business with
or for any other person or entity to any extent whatsoever, other than to the
extent required by the terms and conditions of this Agreement.

               (b) Constructive Termination. Excepting any action precipitated
                   ------------------------
by reason of regulatory requirements as provided in Section 5(b) below,
substantial curtailment of the duties and authority of Kelly as Board Chairman
hereunder by Columbia Bancorp and Columbia Bank shall constitute a termination
without cause in breach of this Agreement.

     4.   Payment Amount; Terms.  As full compensation for all services rendered
          ---------------------
to Columbia Bancorp and Columbia Bank pursuant to this Agreement and the
covenants contained herein, Columbia Bancorp and Columbia Bank shall pay to
Kelly the following:
<PAGE>

          (a)  Base Compensation. Kelly's base compensation (the "Base
               -----------------
Compensation") shall be $60,000 per annum. The Board of Directors shall review
such base compensation at least annually and may grant such raises as in its
discretion are deemed warranted.

                    (1) Base Compensation Rate. Compensation to begin on the
                        ----------------------
     Commencement Date at the above annual rate.

                    (2) Method of Payment. Columbia Bancorp and/or Columbia Bank
                        -----------------
     shall pay Kelly's said base compensation in equal monthly installments or
     more frequently.

          (b) Vacation and Leave. Kelly shall be entitled to such vacation and
              ------------------
leave as may be provided for under the current and future leave and vacation
policies of Columbia Bancorp and Columbia Bank for executive officers.

          (c) Office Space. Columbia Bancorp will provide customary executive
              ------------
office space and executive office support to Kelly beginning on the Commencement
Date.

          (d) D & O Insurance. Columbia Bancorp and Columbia Bank will provide
              ---------------

Kelly with directors and officers liability insurance coverage on terms
comparable to that provided to Columbia Bancorp's and Columbia Bank's other
officers and directors.

          (e) Additional Compensation. Upon the earlier to occur of (i) any sale
              -----------------------
or exchange of stock in Columbia Bancorp with any third party which results in a
change in a controlling interest of Columbia Bancorp, or (ii) five years from
the Commencement Date, Columbia Bancorp shall thereupon immediately pay to Kelly
the sum of $200,000 as additional compensation to Kelly or his heirs. In
addition, in the event Columbia is required to pay such additional compensation
as a result of a change in a controlling interest of Columbia Bancorp and such a
change in a controlling interest occurs prior to the time when Kelly shall have
become fully vested in any stock option plan established for his benefit, Kelly
shall thereupon also become immediately vested in all options theretofore issued
to him or accrued to his benefit. For purposes of construing the foregoing, the
term "change in a controlling interest" shall be defined as provided in
applicable Federal Reserve Board regulations.
<PAGE>

          5.  Rights to Terminate Agreement.

          (a) Breach or Default Under Agreement. Either party may terminate this
              ---------------------------------
Agreement for breach or default as provided herein below.

          (b) Termination Without Cause/Severance.  Kelly may terminate this
              -----------------------------------
Agreement in accordance with Paragraph 2(a)(1)(A), above.  Columbia Bancorp and
Columbia Bank may terminate this Agreement in accordance with Paragraph
2(a)(l)(B), above.  Otherwise, if Kelly is not in breach or default of this
Agreement and Columbia Bancorp or Columbia Bank terminates Kelly's services for
any reason and under any procedures other than those specified in paragraph (c),
below, then Columbia Bancorp or Columbia Bank shall thereupon immediately pay to
Kelly the sum of $120,000 as severance compensation to Kelly; being equal to
twice his Base Compensation for a 12 month period.  In addition, should such
termination occur prior to the time when Kelly shall have become fully vested in
any stock option plan established for his benefit, Kelly shall thereupon also
become immediately vested in all options theretofore issued to him or accrued to
his benefit.

          (c) Termination of Kelly With Cause; Procedure.
              ------------------------------------------

                 (1) Termination of Compensation. If Columbia Bancorp and
                     ---------------------------
     Columbia Bank terminates Kelly for cause as set forth in this paragraph,
     then the compensation payments provided for herein shall cease.

                 (2) Definition of Cause. Under this Agreement, "cause" shall be
                     -------------------
     defined to be:

                         (A) Any willful act or action on the part of Kelly done
          in connection with or associated with the services rendered by Kelly
          under this Agreement for which a criminal prosecution (other than
          traffic and misdemeanor actions) is commenced by the prosecuting
          authorities in the jurisdiction in which such act or action occurred.
          For the purposes of this Agreement, the commencement of a criminal
          prosecution shall be deemed to have occurred upon the filing of a
          criminal information against Kelly or the indictment of Kelly by any
          local, state or federal authority.

                         (B) Any act of theft, fraud, deceit, material
          misrepresentation, assault or battery done by Kelly in connection with
          or associated with the services rendered by Kelly to Columbia Bancorp
          or Columbia Bank under this Agreement.

                         (C) Any act, action, failure to act or omission which
          constitutes gross misconduct or gross negligence in connection with or
          associated with the services rendered by Kelly under this Agreement,
          provided that the procedures of paragraph 5(c)(3) are followed.

                         (D) Any termination following a default of this
          Agreement by Kelly, pursuant to the provisions of Paragraph 10 below.

                         (E) Any Bank Regulatory Agency action with respect to
          this Agreement, or any failure of this Agreement to comply with any
          Bank Regulatory Agency requirements.
<PAGE>

              (3) Procedure for Termination With Cause.  The procedure for
                  ------------------------------------
     termination with cause shall be as follows:

                    (A) For any reason specified in paragraph 5(c)(2)(A), Kelly
          shall be terminated upon the commencement of prosecution, as of the
          date of the act to which that paragraph applies.

                    (B) For any reason specified in Paragraphs 5(c)(2)(B),
          5(c)(2)(C), 5(c)(2)(D) or 5(c)(2)(E), unless ordered by or agreed to
          differently between Columbia Bancorp and/or Columbia Bank, and a Bank
          Regulatory Agency, or unless a criminal prosecution has commenced as
          provided in Paragraphs 5(c)(2)(A) and 5(c)(3)(A) above, Columbia
          Bancorp and/or Columbia Bank shall give Kelly written notice of the
          cause alleged to be the basis for Kelly's termination.  Kelly shall
          thereafter have a period of 30 days from the date of the receipt of
          Columbia Bancorp's and/or Columbia Bank's written notice in which to
          dispute and/or explain the situation(s) referred to in Columbia
          Bancorp's and/or Columbia Bank's written noticed, including, if
          appropriate, a response to Bank Regulatory Agencies.  If Kelly does
          not respond to Columbia Bancorp's and/or Columbia Bank's notice, Kelly
          shall be deemed to have agreed to Columbia Bancorp's and/or Columbia
          Bank's and/or the Bank Regulatory Agency's allegations and the
          termination shall be effective as of the date of Columbia Bancorp's
          and/or Columbia Bank's written notice.  If Kelly disputes the
          allegations contained in Columbia Bancorp's and/or Columbia Bank's
          and/or the Bank Regulatory Agency's notice, Kelly shall notify
          Columbia Bancorp and/or Columbia Bank in writing within the time
          period set forth above and Columbia Bancorp and/or Columbia Bank and
          Kelly shall set a meeting to discuss a resolution of the dispute.  If
          the parties and/or any Bank Regulatory Agency do not reach agreement
          as to Kelly's termination, within 45 days of Columbia Bancorp's and/or
          Columbia Bank's notice, Columbia Bancorp and/or Columbia Bank, by a
          majority of its Board of Directors, shall have the right to terminate
          Kelly and to discontinue the compensation payments to Kelly.  If Kelly
          nevertheless still disagrees that his termination was proper under the
          terms of this Agreement, both parties hereto by their execution hereof
          agree, unless otherwise ordered by or agreed to differently between
          any Bank Regulatory Agency and Columbia Bancorp and/or Columbia Bank,
          to submit to binding arbitration under the rules, regulations and
          procedures of the American Arbitration Association.

          (d) Termination of Agreement by Kelly for Cause.  If Columbia Bancorp
              -------------------------------------------
and/or Columbia Bank shall become in breach or default of any of the material
provisions hereof, including especially any constructive termination [as
provided in Paragraph 3(b), above] and fails to cure such breach as provided in
Paragraph 10, below, then Kelly may, at his option at any time thereafter, elect
to terminate this Agreement for cause, in which event Columbia Bancorp or
Columbia Bank shall thereupon immediately pay to Kelly the sum of $60,000 as
severance compensation to Kelly; being equal to his Base Compensation for a 12
month period.  In addition, should such termination occur prior to the time when
Kelly shall have become fully vested in any stock option plan established for
his benefit, Kelly shall thereupon also become immediately vested in all options
theretofore issued to him or accrued to his benefit.
<PAGE>

          (e) Death or Disability.  If Kelly should be unable to perform his
              -------------------
professional duties due to disability, then the compensation provided for
hereinabove shall continue at its full level for a period not to exceed 120 days
and, if the disability is temporary, shall resume upon Kelly's return to his
duties hereunder.  In the event of Kelly's death, such compensation payments
shall cease.

          (f) Survival of Restrictions. In the event of a termination of the
              ------------------------
offer set forth in this Agreement, or in the event of a termination of this
Agreement after acceptance hereof by Kelly, all covenants and restrictions
contained herein shall survive the termination and shall continue in full force
and effect as provided for herein.

     6. Representations and Warranties of Kelly.  Kelly represents and warrants
        ---------------------------------------
to Columbia Bancorp and Columbia Bank the following:

          (a) Information Supplied to Columbia Bancorp and Columbia Bank.  All
              ----------------------------------------------------------
information and data, including but not limited to, personal data, work
histories, salaries and responsibilities, represented and provided to Columbia
Bancorp and Columbia Bank by Kelly in his application for the position provided
for herein are true and correct in all material respects and Kelly has not
stated any facts or circumstances, nor has he failed to disclose any facts or
circumstances to Columbia Bancorp and Columbia Bank the statement or omission of
which would cause Kelly's application to be false or misleading in any material
respect.

          (b) Prior Agreements.  Kelly is not now a party to or bound by any
              ----------------
employment, consulting or other type of agreement, nor has he been a party to or
bound by any such agreement, which would be breached by, or of which Kelly would
be in default, by virtue of any provision contained in this Agreement with
Columbia Bancorp and Columbia Bank, nor is Kelly a party to any such agreement
which would compete with or constitute a conflict of interest with this
Agreement and Kelly's duties and obligations to Columbia Bancorp and Columbia
Bank.

          (c) Bank Regulatory Agency Approval. To the best of Kelly's knowledge,
              -------------------------------
information and belief, there are no facts or circumstances contained in Kelly's
personal or professional history which are likely to, or which in fact will,
cause any Bank Regulatory Agency having jurisdiction over Columbia Bancorp or
Columbia Bank to withdraw, suspend or substantially modify its approval of Kelly
as BOARD CHAIRMAN of Columbia Bancorp or Columbia Bank.

     7. Representations and Warranties of Columbia Bancorp and Columbia Bank.
        --------------------------------------------------------------------

          To the best of Columbia Bancorp's and Columbia Bank's knowledge,
information and belief, there are no facts or circumstances to which Columbia
Bancorp or Columbia Bank is privy, which are likely to, or which in fact will,
cause any Bank Regulatory Agency having jurisdiction over Columbia Bancorp or
Columbia Bank to withdraw, suspend or substantially modify its approval of Kelly
as BOARD CHAIRMAN of Columbia Bancorp and Columbia Bank.

     8. Restrictive Covenants.
        ---------------------

          (a) Proprietary Information. Kelly acknowledges that upon acceptance
              -----------------------
of this Agreement, Kelly will be making use of, acquiring and adding to Columbia
Bancorp's and Columbia Bank's confidential and proprietary information of a
special and unique nature and value relating to such matters as, but not limited
to Columbia Bancorp's and Columbia Bank's business operations, internal
<PAGE>

structure, financial affairs, programs, software, systems, procedures, manuals,
confidential reports, and sales and marketing methods, as well as the amount,
nature and type of services, equipment and methods used and preferred by
Columbia Bancorp's and Columbia Bank's suppliers, and customers, all of which
shall be deemed to be confidential information. Kelly acknowledges that such
confidential information has been and will continue to be of central importance
to the business of Columbia Bancorp and Columbia Bank and that disclosure of it
or its use by others could cause substantial loss to Columbia Bancorp and
Columbia Bank. In consideration of his anticipated and thereafter continued
contract with Columbia Bancorp and Columbia Bank, upon acceptance hereof, Kelly
agrees that during the entire term of this Agreement, and upon and for a period
of two years after such term, Kelly shall not, for any purpose whatsoever,
directly or indirectly, divulge, reveal, report, publish, transfer, or disclose
to any person or entity any of such confidential information which was obtained
by Kelly as a result of Kelly's services to Columbia Bancorp and Columbia Bank,
nor shall Kelly reveal to any person or entity any trade secrets of Columbia
Bancorp or Columbia Bank, but Kelly shall hold all of the same confidential and
inviolate. For purposes of construing the foregoing, "proprietary information"
shall not be construed to include information generally available in the public
domain through sources other than Kelly.

          (b) Property of Columbia Bancorp or Columbia Bank.  All contracts,
              ---------------------------------------------
agreements, forms, financial books, records, instruments and documents, supplier
lists, memoranda, data, reports, programs, software, tapes, rolodexes, telephone
and address books, letters, research, listings, programming, and any other
instruments, records or documents relating or pertaining to Columbia Bancorp or
Columbia Bank (hereinafter referred to as "Records") shall at all times be and
remain the property of Columbia Bancorp and Columbia Bank.  Upon termination or
expiration of the term of this Agreement for any reason whatsoever, Kelly shall
return to Columbia Bancorp or Columbia Bank all Records (whether furnished by
Columbia Bancorp, by Columbia Bank, by a third party or prepared by Kelly), and
Kelly shall neither make nor retain any copies of any such Records after such
termination.

          (c) Inventions and Creations. All inventions and other creations,
              ------------------------
whether or not patentable or copyrightable, and all ideas, reports and other
creative works, including, without limitation, innovations, manuals or other
materials, made or conceived in whole or in part by Kelly during the term of
this Agreement, which relate in any manner whatsoever to the business, existing
or proposed of Columbia Bancorp, Columbia Bank or any other business or research
development effort in which Columbia Bancorp or any of its subsidiaries or
affiliates engages during the term of this Agreement, will be disclosed promptly
by Kelly to Columbia Bancorp and Columbia Bank and shall be the sole and
exclusive property of Columbia Bancorp and Columbia Bank.

          (d) Non-Solicitation of Customers and Employees. Kelly agrees during
              -------------------------------------------
the term of this Agreement and for a period of two years immediately following
the expiration of the term hereof, that he shall not for his account or on
behalf of any other person or legal entity, hire or solicit to hire any employee
of Columbia Bancorp (or any of its affiliates or subsidiaries) or solicit the
banking business of any person or entity known to him to be a customer of
Columbia Bancorp (or any of its affiliates or subsidiaries).

     9. Indemnification.  Kelly agrees to indemnify and hold harmless Columbia
        ---------------
Bancorp and Columbia Bank from and against any and all claims made against
Columbia Bancorp and Columbia Bank by any party by virtue of Kelly's past
employment, whether such claims are made by a past employer or by another party
with whom Kelly has dealt in the past.  Columbia Bancorp and Columbia Bank agree
to indemnify and hold harmless Kelly from and against any and all claims made
against Kelly arising
<PAGE>

directly or indirectly from any fact or matter which contradicts (or as alleged
would contradict) any representation or warranty of Columbia Bancorp and
Columbia Bank hereunder. Promptly after receipt of any party hereto (the
"Indemnitee") of notice of any demand, claim or circumstance which, or which
with the lapse of time, would or might give rise to a claim or the commencement
(or threatened commencement) of any action, proceeding pr investigation (an
"Asserted Liability") that may result in a loss, the Indemnitee shall give
notice thereof (the "Claims Notice") to the other party (the "Indemnifying
Party"). The Claims Notice shall describe the Asserted Liability in reasonable
detail, and shall indicate the amount (estimated, if necessary and to the extent
feasible) of the loss that has been or may be suffered by the Indemnitee. The
Indemnifying Party may elect to assume responsibility for and to compromise or
defend, at its own expense and by its own counsel (which counsel shall be
reasonably satisfactory to the Indemnitee), any Asserted Liability, unless in
the reasonable judgment of the Indemnitee there may be one or more legal
defenses available to it that are different from or in addition to those
available to the Indemnifying Party and, therefore, it is advisable for the
Indemnitee to be represented by separate counsel. Then, in such event, the
Indemnitee shall have the right to employ separate counsel to represent it
(which shall be reasonably satisfactory to the Indemnifying Party), in which
event the fees and disbursements of such counsel shall be subject to
indemnification hereunder. If such Indemnifying Party elects to compromise or
defend such Asserted Liability, it shall within 30 days (or sooner, if the
nature of the Asserted Liability so requires) notify the Indemnitee of its
intent to do so, and the Indemnitee shall have no further liability for such
Asserted Liability but shall cooperate, at the expense of the Indemnifying
Party, in the compromise of, or defense against, such Asserted Liability. If the
Indemnifying Party elects not to compromise or defend the Asserted Liability,
fails to notify the Indemnitee of its election as herein provided, or contests
its obligation to indemnify under this Agreement, the Indemnitee may pay,
compromise or defend such Asserted Liability. Notwithstanding the foregoing,
neither the Indemnifying Party nor the Indemnitee may settle or compromise any
claim over the objection of the other; provided, however, that consent to
settlement or compromise shall not be unreasonably withheld. In any event, the
Indemnitee and the Indemnifying Party may participate, at their own expense, in
the defense of such Asserted Liability. If the Indemnifying Party chooses to
defend any claim, the Indemnitee shall make available to the Indemnifying Party
any books, records or other documents within its control that are necessary or
appropriate for such defense.

     10.  Right to Cure; Default.  In the event either party shall be alleged to
          ----------------------
be in breach of this Agreement, written notice shall be given by the other party
and a 10 day opportunity to cure shall be provided.  After such 10 day cure
period, if the breach is not cured and remains as alleged, the breaching party
shall be deemed in default and this Agreement may be terminated in the manner
provided in Paragraph 5, above.

     11.  Entire Agreement. This Agreement represents the entire agreement of
          ----------------
the parties relating to the services of Kelly. All prior negotiations between
the parties are merged into this Agreement and there are no understandings or
agreements other than those incorporated herein.

     12.  Miscellaneous.
          -------------

             (a) Severability; Court Enforcement. The parties hereto covenant
                 -------------------------------
and agree that to the extent any provisions or portion of this Agreement shall
be held, found or deemed to be unreasonable, unlawful or unenforceable, by any
Court of law, then the parties hereto expressly covenant and agree that any such
provision or portion thereof shall be modified to the extent necessary in order
that any such provision or portion thereof shall be legally enforceable to the
fullest extent permitted by applicable law
<PAGE>

and that any court of competent jurisdiction shall, and the parties hereto do
hereby expressly authorize any court of competent jurisdiction to, enforce any
such provision or portion thereof or to modify any such provision thereof shall
be enforced by such court to the fullest extent permitted by applicable law.

          (b) Waiver. Columbia Bancorp and Columbia Bank and Kelly each reserve
              ------
the right to waive any of the terms of this Agreement which benefits the party
waiving same. Any such waiver must be in a writing signed by the party waiving
the same.

          (c) Choice of Law. It is the intention of the parties hereto that this
              -------------
Agreement shall be governed by the laws of the State of Maryland.

          (d) Successors. The terms of this Agreement shall inure to the benefit
              ----------
of and be binding upon Columbia Bancorp and Columbia Bank, their successors and
assigns, and upon Kelly, his heirs, guardians and personal and legal
representatives.

          (e) Gender. The use of the masculine gender herein shall be deemed to
              ------
be or include the feminine gender, wherever appropriate.

          (f) Notices. All notices, demands and other communications hereunder
              -------
shall be in writing and shall be deemed to have been duly given if delivered
personally or if sent registered or certified mail, return receipt requested,
properly addressed and postage prepaid to the addresses set forth hereinabove.

          (g) Counterparts.  This Agreement may be executed in one or more
              ------------
counterparts, each of which shall be deemed to be an original, but all of which
together shall constitute one and the same instrument.

          (h) Headings.  The Section and paragraph headings used herein are for
              --------
convenience and reference only and shall not enter into the interpretation
hereof.

          (i) Representation by Counsel. The parties hereto acknowledge that
              -------------------------
James J. Winn, Jr., of the law firm of Piper & Marbury, L.L.P., has acted as
counsel to Columbia Bancorp and Columbia Bank in this matter.
<PAGE>

     IN WITNESS WHEREOF this Agreement has been executed by the undersigned as
of the day and year first above written.

ATTEST/WITNESS:                     COLUMBIA BANCORP

_______________________________     By:________________________________
                                         President

                                    THE COLUMBIA BANK

_______________________________     By:________________________________
                                         President

_______________________________     ___________________________________
                                         Winfield M. Kelly, Jr.

<PAGE>

                                                                   Exhibit 10.14

                              EMPLOYMENT AGREEMENT

     EMPLOYMENT AGREEMENT, dated as of __________________, between THE COLUMBIA
BANK, a Maryland trust company and a principal subsidiary of COLUMBIA BANCORP, a
Maryland corporation, (the "Bank"), and Stephen A. Horvath. (the "Executive").
The Employment Agreement dated as of December 9, 1996, between the Bank as
successor in interest to Suburban Bank of Maryland and the Executive, is hereby
terminated effective with the execution of this Employment Agreement.

                              W I T N E S S E T H:
                              - - - - - - - - - -

     The Executive will serve as the Executive Vice President - Washington
Region of the Bank and will possess an intimate knowledge of the business and
affairs of the Bank.  The Bank recognizes the Executive's contribution to the
organization and its predecessor by merger, Suburban Bank of Maryland, growth
and success of the Bank and desire to enter into an employment agreement with
the Executive in order to assure to the Bank the benefits of the Executive's
expertise and knowledge.  The Executive, in turn, desires to enter into full-
time employment with the Bank on the terms provided herein.

     Accordingly, in consideration of the mutual covenants and representations
contained herein and the mutual benefits derived herefrom, the parties hereto
agree as follows:

          1.    Full-Time Employment of Executive.
                ----------------------------------

          1.1. Duties and Status.
               -----------------

               (a)  The Bank hereby engages the Executive as a full-time
       executive employee for the period (the "Employment Period") specified in
       paragraph 4.1, and the Executive accepts such employment, on the terms
       and conditions set forth in this Agreement. During the Employment Period,
       the Executive shall exercise authority and perform executive duties as an
       Executive Vice President of the Bank.

               (b)  During the Employment Period, the Executive shall (i) not
       engage in consulting work or any trade or business for his own account or
       for or on behalf of any other person, firm or corporation which competes,
       conflicts or materially interferes with the performance of his duties
       hereunder in any way and (ii) accept such additional office or offices to
       which he may be elected by the Board of Directors of the Bank, provided
       that the performance of the duties of such office or offices shall be
       consistent with the scope of the duties provided for in paragraph 1.1(a).

               (c)  The Executive shall be required to perform the services and
       duties provided for in paragraph 1.1(a) only at the principal office of
       the Bank in Columbia, Maryland, or at such other locations acceptable to
       the Executive. The Executive shall be entitled to vacation, leave of
       absence, and leave for illness or temporary disability in accordance with
       the policies to be established for the Bank, which shall be similar to
       those commonly offered at comparable
<PAGE>

       banking institutions, and any leave on account of illness or temporary
       disability shall not constitute a breach by the Executive of his
       agreements hereunder.

       1.2.  Compensation and General Benefits.  As compensation for his
             ---------------------------------
     services under this Agreement, the Executive shall be compensated as
     follows:

             (a)  The Bank shall pay the Executive an annual salary which is not
       less than the greater of (i) a base salary of $150,000.00 per annum, or
       (ii) any subsequently established higher annual base salary. Such salary
       shall be payable in periodic equal installments which are no less
       frequent than monthly. Such salary shall be subject to normal periodic
       review at least annually for increases based on the salary policies of
       the Bank and contributions to the enterprises.

             (b)  The Executive shall be entitled to participate in such
       pension, profit sharing, stock incentive, stock option, stock purchase,
       incentive, group and individual disability, group and individual life,
       survivor income, sickness, accident, dental, medical or health insurance
       and other plans of the Bank which are in effect immediately prior to the
       effective date of this Agreement or in any other or additional benefit
       programs, plans or arrangements of the Bank which may be established by
       the Bank, as and to the extent any such benefit programs, plans or
       arrangements are or may from time to time be in effect, as determined by
       the Bank and terms hereof. The Bank shall neither (i) terminate or amend
       any benefit program, plan or arrangement of the Bank pursuant to which
       the Executive, or his dependents, beneficiaries or estate, is or shall be
       entitled to benefits, nor (ii) terminate or amend any formula or method
       set forth in any benefit program, plan or arrangement of the Bank
       pursuant to which the amount and type of benefits to which the Executive,
       or his dependents, beneficiaries or estate, is or shall be entitled
       thereunder are determined, if such termination or amendment would in any
       way modify or deprive the Executive, or his dependents, beneficiaries or
       estate, of any benefits to which he, or his dependents, beneficiaries or
       estate, is or shall be entitled under any benefit program, plan or
       arrangement of the Bank, unless (a) the Executive expressly consents in
       writing to such termination or amendment or (B) the amendment is required
       by law or regulation and the Bank shall, to the extent necessary,
       provide, pay or provide for payment of amounts equal to any benefits lost
       or reduced by such amendment. Throughout the period of his employment
       hereunder, the Executive shall be entitled to the receipt of any personal
       benefits from the Bank at the Bank's expense including, but not limited
       to, any other perquisites provided by the Bank to executives with
       comparable authority or duties. The term "benefit programs, plans, or
       arrangements of the Bank" as used in this Agreement refers to the matters
       in this paragraph 1.2(b).

       2.   Competition; Confidential Information.  The Executive and the Bank
            -------------------------------------
recognize that due to the nature of his association with the Bank and of his
engagements hereunder, and the relationship of the Executive to the Bank, both
in the past as an organizer and in the future hereunder, the Executive has had
access to and has acquired, will have access to and will acquire, and has
assisted in and may assist in developing, confidential and proprietary
information relating to the business and operations of the Bank and its
affiliates, including, without limiting the generality of the foregoing,
information with respect to its present and prospective systems, customers,
agents, accounts, deposits, loans, and sales and marketing methods.  The
Executive acknowledges that such information has been and will continue to be of
central importance to the business of the Bank and its affiliates and that
disclosure of it to or its use by
<PAGE>

others could cause substantial loss to the Bank. The Executive and the Bank also
recognize that an important part of the Executive's duties will be to develop
goodwill for the Bank and its affiliates through his personal contact with
customers, agents and others having business relationships with the Bank and its
affiliates, and that there is a danger that this goodwill, a proprietary asset
of the Bank and its affiliates, may follow the Executive if and when his
relationship with the Bank is terminated. The Executive accordingly agrees as
follows:

               2.1. Non-Competition.
                    ---------------

                    (a)  During the Non-Competition Period, the Executive will
          not, directly or indirectly, either individually or as owner, partner,
          agent, employee, consultant or otherwise, except for the account of
          and on behalf of the Bank or its affiliates ("affiliates" is defined
          solely for purposes of this paragraph 2 as "Columbia Bancorp and its
          subsidiaries"), engage in any activity competitive with the business
          of the Bank or its affiliates, nor during the Non-Competition Period
          will he, in competition with the Bank or its affiliates, solicit or
          otherwise attempt to establish for himself or any other person, firm
          or entity, any business relationships with any person, firm or
          corporation which was, at any time during the Non-Competition Period,
          (i) a state or national bank, (ii) a bank holding company, or (iii) a
          direct or indirect subsidiary of a state or national bank or a bank
          holding company, in each case which has its principal operations
          located in Howard County, Montgomery County and Prince George's
          County, Maryland or within a 15 mile radius of the principal office of
          the Corporation in Columbia, Maryland, excepting both the City of
          Baltimore and Washington, D.C.

                    (b)  The Non-Competition Period shall commence on the date
          of this Agreement and shall terminate on:

                         (i)   The date of the termination of the Employment
                    Period; or

                         (ii)  If the Executive resigns in circumstances other
                    than those described in paragraph 4.3(a)(ii), two years
                    after the date of such resignation; provided, however, that
                    if the Executive resigns during a Change in Control Period
                    in circumstances other than those described in paragraph
                    4.3(a)(ii), the Non-Competition Period shall terminate on
                    the date of such resignation; or

                         (iii) If the Executive is terminated for cause (as
                    defined in paragraph 4.3(b)), two years after the date of
                    such termination for cause.

               (c)  Nothing in this paragraph 2 shall be construed to prevent
          the Executive from owning, as an investment, not more than 1% of a
          class of equity securities issued by any issuer and publicly traded
          and registered under Section 12 of the Securities Exchange Act of
          1934.

          2.2.  Trade Secrets.  The Executive will keep confidential any trade
                -------------
          secrets or confidential or proprietary information of the Bank and its
          affiliates which are now known to him or which hereafter may become
          known to him as a result of his employment or association with the
          Bank and shall not at any time directly or indirectly disclose any
          such information to any person, firm or corporation, or use the same
          in any way other than in connection with the business of the Bank or
          its affiliates during and at all times after the expiration of the
<PAGE>

          Employment Period.  For purposes of this Agreement, "trade secrets or
          confidential or proprietary information" means information unique to
          the Bank or any of its affiliates which has a significant business
          purpose and is not known or generally available from sources outside
          the Bank or any of its affiliates or typical of industry practice.

          3.   Bank's Remedies for Breach.  It is recognized that damages in the
               --------------------------
event of breach of paragraph 2 by the Executive would be difficult, if not
impossible, to ascertain, and it is therefore agreed that the Bank, in addition
to and without limiting any other remedy or right it may have, shall have the
right to an injunction or other equitable relief in any federal or state court
of competent jurisdiction in the State of Maryland, enjoining any such breach,
and the Executive hereby waives any and all defenses he may have on the ground
of lack of jurisdiction or competence of the court to grant such an injunction
or other equitable relief.  The existence of this right shall not preclude any
other rights and remedies at law or in equity which the Bank may have.  In the
event the Bank seeks an injunction against the Executive and lose, then the Bank
shall be liable for damages and for any legal fees incurred by the Executive in
defending the action.

          4.   Employment Period.
               -----------------

          4.1. Duration. The Employment Period shall commence on the date of
               --------
          this Agreement (the "Effective Date") and shall continue until the
          earlier of (i) the close of business on the date which is two years
          after the date on which, during the Employment Period, the Bank gives
          written notice of termination to the Executive or the Executive gives
          written notice of termination to the Bank but not later than the close
          of business on [65/th/ Birthday] (ii) termination of this Agreement
          (as defined in paragraph 4.3(a)), (iii) death of the Executive, (iv)
          total disability of the Executive (as defined in paragraph 4.3(c)),
          (v) resignation of the Executive in circumstances other than those
          described under paragraph 4.3(a)(ii), or (vi) discharge of the
          Executive for cause (as defined in paragraph 4.3(b)).

          4.2. Payments after Employment Period.
               --------------------------------

                    (a)  In the event of a termination of this Agreement under
               paragraph 4.1(ii), the Bank shall pay to the Executive and
               provide him with the following:

                           (i) During the remainder of the Employment Period
                    (determined without regard to paragraph 4.1(ii)), but not
                    less than one year following the occurrence of any event of
                    termination under paragraph 4.1(ii), the Bank shall continue
                    to pay the Executive his salary at the rate and as required
                    by paragraph 1.2(a) and in effect immediately prior to the
                    date of termination plus (in any year after the first year)
                    an annual bonus payable at the time or times customary
                    during the Employment Period, which bonus shall be
                    equivalent to a certain percentage of his salary paid to him
                    by the Bank for each such year during the remainder of the
                    Employment Period (determined without regard to paragraph
                    4.1(ii) but with regard to paragraphs 4.1(iii) and (iv)),
                    such percentage to be equal to the average of the percentage
                    of his salary which his annual bonus represented during each
                    of the three years immediately preceding termination of this
                    Agreement.

                         (ii)  During the remainder of the Employment Period
                    (determined without regard to paragraph 4.1(ii) but with
                    regard to paragraphs 4.1(iii) and
<PAGE>

                    (iv)), the Executive shall continue to be treated as an
                    executive (at the level provided for in paragraph 1.1(a))
                    under all of the benefit programs, plans or arrangements of
                    the Bank described in paragraph 1.2(b). In addition, the
                    Executive shall continue to be entitled to all benefits and
                    service credits for benefits under all of the benefit
                    programs, plans or arrangements of the Bank described in
                    paragraph 1.2(d) as if he were still employed during such
                    period under this Agreement.

                         (iii)  If, despite the provisions of subparagraph (ii)
                    above, benefits, service credits, or the right to accrue
                    further benefits or service credits under any benefit
                    programs, plans or arrangements of the Bank described in
                    paragraph 1.2(b) shall not be payable or provided to the
                    Executive, or his dependents, beneficiaries and estate,
                    because he is not longer an employee of one or both of the
                    Bank, the Bank shall, to the extent necessary, provide, pay
                    or provide for payment of equivalent benefits, service
                    credits and rights to accrue further benefits or service
                    credits to or for the benefit of the Executive, his
                    dependents, beneficiaries and estate.

                    (b)  In the event of a termination of this Agreement under
                 paragraph 4.1(ii), the Executive in his discretion may elect,
                 within 60 days after such termination, to be paid a lump sum or
                 other agreed severance allowance in lieu of termination
                 payments provided for in paragraph 4.2(a) in an amount of cash
                 which shall be negotiated and agreed upon in writing between
                 the Executive and the Bank. Among the forms which the severance
                 allowance may take, if negotiated and agreed upon in writing
                 between the Executive and the Bank, shall be payment of equal
                 installments to the Executive the present value of which,
                 computed at the time required by Section 4999 of the Internal
                 Revenue Code of 1986 (the "Code"), is below the threshold
                 necessary to trigger applicability of Section 4999 of the Code
                 which imposes a nondeductible excise tax on any recipient of an
                 "excess parachute payment" equal to 20% of the amount of such
                 payment. In the event that the Executive makes an election
                 pursuant to this paragraph 4.2(b), the severance allowance
                 shall represent the present fair market value of the amount of
                 salary, bonuses and all benefit programs, plans and
                 arrangements of the Bank which the Executive would be entitled
                 to during the Employment Period (determined without regard to
                 paragraph 4.1(iii)) under this Agreement. Upon the date that
                 the Bank and the Executive enter into a written agreement
                 providing for a severance payment, the Bank's obligations to
                 the Executive pursuant to paragraph 4.2(a) shall terminate. In
                 the event that the Executive and the Bank are unable to
                 negotiate a mutually satisfactory agreement concerning the
                 amount of a severance payment pursuant to this paragraph
                 4.2(b), then the Executive shall receive termination payments
                 and benefits as provided in paragraphs 4.2(a). Payments made
                 under this paragraph 4.2(b) shall continue notwithstanding the
                 subsequent death or disability of the Executive.

                    (c)  In the event of a termination of this Agreement under
                 paragraph 4.1(iii), (i) the Bank shall pay the Executive's
                 estate an amount equal to six months' salary at the rate and as
                 required by paragraph 1.2(a) and in effect immediately prior to
                 the date of death, (ii) the Bank shall continue benefits under
                 the Bank's sickness, accident or
<PAGE>

                 health insurance for a period of six months following death of
                 the Executive for those dependents and beneficiaries of the
                 Executive who were covered by such programs, plans or
                 arrangements at the date of the Executive's death, and (iii)
                 the Executive's dependents, beneficiaries and estate, as the
                 case may be, will receive such survivor and other benefits as
                 they may be entitled under the terms of the benefit programs,
                 plans, and arrangements described in paragraph 1.2(b) which
                 provide benefits upon death of the Executive.

                    (d)  In the event of a termination of this Agreement under
                 paragraph 4.1(iv), (i) the Bank shall pay the Executive an
                 amount equal to six months' salary at the rate and as required
                 by paragraph 1.2(a) and in effect immediately prior to the date
                 of total disability, (ii) the Bank shall continue benefits
                 under the Bank's sickness, accident and health insurance for
                 two years following the date of total disability for the
                 Executive and his dependents and beneficiaries who are covered
                 by such programs, plans and arrangements during the two-year
                 period; and (iii) the Executive, and his dependents,
                 beneficiaries and estate, as the case may be, will receive such
                 benefits as they may be entitled under the terms of the benefit
                 programs, plans, and arrangements described in paragraph 1.2(b)
                 which provided benefits upon total disability of the Executive.

                    (e)  In the event of a termination of this Agreement under
                 paragraph 4.1(v) or (vi), the Executive, and his dependents,
                 beneficiaries and estate, as the case may be, will receive such
                 benefits as they may be entitled under the terms of the benefit
                 programs, plans, and arrangements of the Bank described in
                 paragraph 1.2(b) which provide benefits upon retirement,
                 resignation or discharge for cause, as the case may be.

                    (f)  The Executive shall not be required to mitigate the
                 amount of any payment provided for in this paragraph 4.2 by
                 seeking employment or otherwise, nor shall the amount of any
                 payment provided for in this paragraph 4.2 be reduced by any
                 compensation or remuneration earned by the Executive as the
                 result of employment by another employer, or self-employment,
                 or as a partner, after the date of termination or otherwise.
                 Any payment provided for in this paragraph 4.2 shall be deemed
                 "liquidated damages" rather than a "penalty."

          4.3.   Definitions.  The following words shall have the specified
                 ------------
          meanings when used in the paragraphs specified:

                    (a)  In paragraphs 4.1(ii), 4.2(a) and (b) and 5, the term
                 "termination" means termination (i) by the Bank of the
                 employment of the Executive with the Bank for any reason other
                 than death or total disability of the Executive or other than
                 for cause, or (ii) by resignation of the Executive due to a
                 significant change in the nature or scope of his authorities or
                 duties from those contemplated in paragraph 1.1, a reduction in
                 total compensation from that provided in paragraph 1.2, or the
                 breach by the Bank of any other provision of this Agreement.

                    (b)  In paragraphs 4.1(vi) and 4.3(a)(i), the term "cause"
                 means (i) substantiated fraud, or substantiated
                 misappropriation resulting in material damage to the property
<PAGE>

                 or business of the Bank; conviction for commission of a felony;
                 (ii) continuance of either willful and repeated failure or
                 grossly negligent and repeated failure by the Executive to
                 perform his duties in compliance with this Agreement after
                 written notice to the Executive by the Board of Directors
                 specifying such failure, provided that such "cause" shall have
                 been found by a majority vote of the Board of Directors of the
                 Bank (who are not serving as a designee of a person having an
                 interest in excess of 25% of the outstanding stock of Columbia
                 Bancorp) after at least 10 days' written notice to the
                 Executive specifying the cause proposed to be claimed and after
                 an opportunity for the Executive to be heard at meetings of
                 such Board of Directors; or (iii) a continued violation of
                 paragraph 2 after written notice to the Executive by the Board
                 of Directors specifying such violation and providing the
                 Executive the opportunity to cease such violation within 20
                 days from the date of receipt by the Executive of such notice.

                      (c) In paragraphs 1.1(c), 4.1(iv), 4.2(d) and 4.3(a)(i),
                 the term "total disability" means total disability as defined
                 in the Bank's group and individual disability plans. If there
                 is no such plan, then "total disability" means total disability
                 as defined in the Executive's individual disability policy, and
                 if there is no such policy, as defined in the group disability
                 plan for the law firm of Piper & Marbury l.l.p., 36 South
                 Charles Street, Baltimore, Maryland 21201.

          4.4.   (a)  If prior to the first anniversary date of this Agreement,
          the Executive resigns for any reason, the Bank will pay, or cause to
          be paid, to the Executive an amount equal to one times the Executive's
          annual base salary immediately before the Executive's resignation.

                 (b)  Such payment shall be made in one lump sum within 15
          business days after the Executive's resignation.

              5.      Payments for Termination or Resignation after a Change in
                      ---------------------------------------------------------
                      Control.
                      --------

          5.1.   Definitions.
                 -----------

                 (a)  A "Change in Control," as used in this Agreement, shall be
          deemed to have occurred when:

    (i)   Any person (as such term is used in Sections 13(d) and 14(d) of the
          Securities Exchange Act of 1934, as amended, and the regulations
          promulgated thereunder) is or becomes the beneficial owner, directly
          or indirectly, of 25% or more of the voting equity stock of Columbia
          Bancorp, or any person (as such term is used in Sections 13(d) and
          14(d) of the Securities Exchange Act of 1934, as amended, and the
          regulations promulgated thereunder) other than Columbia Bancorp is or
          becomes the beneficial owner, directly or indirectly, of 25% or more
          of the Common Stock of the Bank; or

                 (ii) Any person (as such term is used in Sections 13(d) and
          14(d) of the Securities Exchange Act of 1934, as amended, and the
          regulations promulgated thereunder) gains control of the election of a
          majority of the Board of Directors of Columbia Bancorp, or any person
          (as such term is used in Sections 13(d) and 14(d) of the Securities
          Exchange Act of
<PAGE>

          1934, as amended, and the regulations promulgated thereunder) other
          than Columbia Bancorp gains control of the election of a majority of
          the Board of Directors of the Bank; or

               (iii) Any person (as such term is used in Sections 13(d) and
          14(d) of the Securities Exchange Act of 1934, as amended, and the
          regulations promulgated thereunder) gains control of the management or
          policies of the Bank; or

               (iv)  the Bank consolidates with, or merges with or into, another
          entity (including a corporation, bank, partnership, trust,
          association, joint venture, pool, syndicate, sole proprietorship,
          unincorporated organization or any other form of entity not
          specifically listed herein) or sells, assigns, conveys, transfers,
          leases or otherwise disposes of all or substantially all of its
          assets, or another such entity consolidates with, or merges with or
          into, the Bank, in any such event pursuant to a transaction in which
          the issued and outstanding shares of the voting equity stock of the
          Bank are converted into or exchanged for cash, securities or other
          property; or

               (v)   during any consecutive two-year period, individuals who at
          the beginning of such period constituted the Board of Directors of the
          Bank (together with any directors who are members of the Board of
          Directors on the date hereof and any new directors whose election by
          such Board of Directors or whose nomination for election by the
          stockholders of the Bank was approved by a vote of 66-2/3% of the
          directors then still in office who were either directors at the
          beginning of such period of whose election or nomination for election
          was previously so approved) cease for any reason to constitute a
          majority of the Board of Directors of the Bank then in office.

               (b)   A "Change in Control Period" shall mean the period
          commencing 90 days before a Change in Control and ending 365 days
          after such Change in Control.

          5.2. Amount of Payments.  Except as provided in paragraph 5.2(e), and
               ------------------
     in lieu of amounts payable under paragraph 4, the Bank will pay the
     Executive the following amounts in the following circumstances:

               (a)  (i)  If the Executive is terminated by the Bank in the
          circumstances described under paragraph 4.3(a)(i), or if the Executive
          resigns during a Change in Control Period in the circumstances
          described under paragraph 4.3(a)(ii), or if during a Change in Control
          Period the Executive resigns in circumstances other than those
          described under paragraph 4.3(a)(ii) without having been offered an
          employment agreement the terms of which are comparable to those of
          this Agreement, the Bank will pay, or cause to be paid, to the
          Executive: (a) if the Executive's termination or resignation occurs
          before the Executive has attained the age of 63 years, an amount equal
          to two times the sum of (i) the Executive's annual base salary
          immediately before the Change in Control and (ii) the average of the
          bonuses paid to the Executive over the past three years (including
          years in which no bonus was awarded); or (b) if the Executive's
          termination or resignation occurs on or after the Executive has
          attained the age of 63 years, an amount equal to the amount set forth
          in paragraph 5.2(a)(i)(a) multiplied by a fraction, the numerator of
          which shall be 730 minus the number of days which have passed since
          the Executive's 63rd birthday, and the denominator of which shall be
          730.
<PAGE>

                    (ii)  Such payment shall be made in one lump sum within 15
          business days after the Executive's termination or resignation.

               (b)  (i)   If the Executive resigns during a Change in Control
          Period in circumstances other than those described under paragraph
          4.3(a)(ii) after having been offered an employment agreement the terms
          of which are comparable to those of this Agreement, the Bank will pay,
          or cause to be paid, to the Executive: (a) if the Executive's
          resignation occurs before the Executive has attained the age of 64
          years, an amount equal to the sum of (i) the Executive's annual base
          salary immediately before the Change in Control and (ii) the average
          of the bonuses paid to the Executive over the past three years
          (including years in which no bonus was awarded); or (b) if the
          Executive's resignation occurs on or after the Executive has attained
          the age of 64 years, an amount equal to the amount set forth in
          paragraph 5.2(b)(i)(a) multiplied by a fraction, the numerator of
          which shall be 365 minus the number of days which have passed since
          the Executive's 64th birthday, and the denominator of which shall be
          365.

                    (ii)  Such payment shall be made in one lump sum within 15
          business days after the Executive's resignation.

               (c)  Except as provided in paragraph 5.2(e), if the Executive is
          terminated by the Bank or resigns as described in paragraph 5.2(a), or
          resigns as described in paragraph 5.2(b), the Executive shall continue
          to receive all health, life, and disability insurance benefits
          available to him pursuant to paragraph 1.2(b) of this Agreement
          immediately before such termination or resignation. The Executive
          shall continue to receive such benefits until the earliest of (a) such
          time as the Executive shall have been receiving substantially similar
          insurance benefits for six months under subsequent employment, (b) 24
          months after the date of a termination or resignation described in
          paragraph 5.2(a) or 12 months after the date of a resignation
          described in paragraph 5.2(b), or (c) such date as the Executive shall
          have attained the age of 65 years.

               (d)  All options granted to the Executive under the Bank's stock
          option award arrangements providing for the granting of options to
          acquire common stock to founders, directors and key employees shall
          immediately become fully vested in the event of a Change in Control.

               (e)  The Executive is to receive no payments under paragraph
          5.2(a) or (b) and no benefits under paragraph 5.2(c) if the Executive
          is terminated during a Change in Control Period after having already
          attained the age of 65 years, or if the Executive is terminated by the
          Bank during a Change in Control Period upon the death or total
          disability of the Executive or for cause. In an instance of death or
          total disability of the Executive, however, the Executive and his
          dependents, beneficiaries and estate shall receive any benefits
          payable to them under paragraphs 4.2 (c) and 4.2 (d).

               (f)  Notwithstanding the foregoing, in the event that any of the
          amounts payable to the Executive under paragraph 5.2 would, if made,
          cause the Executive to have tax under Section 4999 of the Code, the
          Executive may elect, at his discretion, to reduce the amount payable
          to him under paragraph 5.2(a) or (b) by an amount such that the
          aggregate after-
<PAGE>

          tax amounts the Executive will receive under paragraph 5.2 will be
          equal to the aggregate after-tax amounts the Executive would receive
          without the reduction he elected (i.e., the aggregate amounts after
          the application of the tax under Section 4999 of the Code and other
          taxes)."

               6.   Legal Costs.  If (i) the Bank shall fail to pay or provide
                    -----------
for payment of any amounts required to be paid or provided for hereunder at any
time, (ii) the Executive desires to consult with or retain counsel as to any
possible breach by the Bank of this Agreement or as to any of his rights under
this Agreement, or (iii) the Executive desires to retain counsel to review or
negotiate the terms of this Agreement prior to the effective date of this
Agreement, the Executive shall be entitled to consult with counsel, and the Bank
agree to pay the reasonable fees and expenses of independent counsel for the
Executive in reviewing or negotiating this Agreement, advising him or in
bringing any proceedings, or in defending any proceedings, involving the
Executive's rights under this Agreement, such right to reimbursement to be
immediate upon the presentment by Executive of written billings for such
reasonable fees and expenses. The Executive shall be entitled to receive
interest (at the prime rate of interest established from time to time at The
First National Bank of Maryland) on any payments of such expenses, or any other
payments under this Agreement, that are overdue.

               7.   Notices.  Any notice, requests, demands and other
                    -------
communications provided for by this Agreement shall be sufficient if in writing
and if sent by registered or certified mail/return receipt to the Executive at
the last address he has filed in writing with either of the Bank or, in the case
of the Bank, at its principal executive offices.

               8.   Binding Agreement.  This Agreement shall be effective as of
                    -----------------
the date hereof and shall be binding upon and inure to the benefit of the
Executive, his executors, administrators and personal representatives. The
rights and obligations of the Corporation and of the Bank under this Agreement
shall inure to the benefit of and shall be binding upon the Bank, and shall be
transferred to and be binding upon any successor of the Bank including, but not
limited to, any successor of the Bank pursuant to a merger, conversion,
consolidation, or transfer of assets; provided, that this Agreement may not be
assigned by the Bank without the consent of the Executive, and in the case of a
successor by transfer of all or substantially all of the assets of the Bank, or
any other successor in which the Bank does not cease to exist by operation of
the transaction in question as a matter of law, the Bank shall not be relieved
of its obligations hereunder; provided further, that in the case of dissolution
and winding up of the business of the Bank, this Agreement and the obligations
hereunder shall be binding upon the trustee of the Bank's assets.

               9.   Entire Agreement.  This Agreement constitutes the entire
                    ----------------
understanding of the Executive and the Bank with respect to the subject matter
hereof and supersedes any and all prior understandings, written or oral,
including any prior employment agreements between the Bank and the Executive.
This Agreement may not be changed, modified, or discharged orally, but only by
an instrument in writing signed by the parties.  This Agreement shall be
governed by the laws of the State of Maryland and the invalidity or
unenforceability of any provisions hereof shall in no way affect the validity or
enforceability of any other provision.
<PAGE>

          IN WITNESS WHEREOF, the parties have executed and delivered this
Agreement on ____________ _____.

ATTEST:                             THE COLUMBIA BANK


___________________                 ______________________________
                                    John M. Bond, Jr.
                                    President and Chief Executive Officer
WITNESS:


___________________                 ______________________________
                                    Stephen A. Horvath

<PAGE>

                                                                    Exhibit 23.1

             CONSENT OF INDEPENDENT CERTIFIED PUBLIC ACCOUNTANTS
             ---------------------------------------------------


     We hereby consent to the use of our report dated January 8, 1999 relating
to the consolidated financial statements of Suburban Bancshares, Inc.
incorporated herein by reference and to the reference to our firm under the
heading "Experts" in the prospectus.



                                         /s/  Stegman & Company
Baltimore, Maryland
November 30, 1999

<PAGE>

                                                                    Exhibit 23.2

              CONSENT OF INDEPENDENT CERTIFIED PUBLIC ACCOUNTANTS
              ---------------------------------------------------



To Board of Directors
Columbia Bancorp:

We consent to the use of our report incorporated herein by reference and to the
reference to our firm under the heading "Experts" in the prospectus.

                                        /s/ KPMG LLP
                                        KPMG LLP

Baltimore, Maryland
November 30, 1999

<PAGE>

                                                                    Exhibit 23.4

                   CONSENT OF AUSTIN FINANCIAL SERVICES, INC.
                   ------------------------------------------


We hereby consent to the use of our firm's name in the Form S-4 Registration
Statement of Columbia Bancorp relating to the registration of shares of Columbia
Bancorp common stock to be issued in connection with the proposed acquisition of
Suburban Bancshares.  We also consent to the inclusion of our opinion letter as
an Appendix to the proxy statement-prospectus included as part of the Form S-4
Registration Statement, and to the references to our opinion included in the
proxy statement-prospectus.

                                        AUSTIN FINANCIAL SERVICES, INC.



                                        By: /s/ Craig D. Bernard
                                            ____________________________
                                            Craig D. Bernard
                                            Executive Vice President

Date:  November 30, 1999


<PAGE>

                                                                    Exhibit 23.5

                      CONSENT OF DANIELSON ASSOCIATES INC.
                      ------------------------------------


We hereby consent to the use of our firm's name in the Form S-4 Registration
Statement of Columbia Bancorp relating to the registration of shares of Columbia
Bancorp common stock to be issued in connection with the proposed acquisition of
Suburban Bancshares.  We also consent to the inclusion of our opinion letter as
an Appendix to the proxy statement-prospectus included as part of the Form S-4
Registration Statement, and to the references to our opinion included in the
proxy statement-prospectus.

                                              DANIELSON ASSOCIATES INC.



                                              By:   /s/ Arnold Danielson
                                                    _____________________
                                                    Arnold Danielson
                                                    Chairman

Date:  November 30, 1999


<PAGE>

                                                                    Exhibit 24.1
                               POWER OF ATTORNEY

     KNOW ALL MEN BY THESE PRESENTS, that each person whose signature appears
below constitutes and appoints John M. Bond, Jr. and John A. Scaldara, Jr. and
each of them, each with full power to act without the other, his true and lawful
attorneys-in-fact and agents, with full powers of substitution and
resubstitution, for him and in his name, place and stead, in any and all
capacities, to sign any or all amendments to this Registration Statement on Form
S-4 and to file the same, with all exhibits thereto, and other documents in
connection therewith, with the Securities and Exchange Commission, granting unto
said attorneys-in-fact and agents full power and authority to do and perform
each and every act and thing requisite and necessary to be done in and about the
premises, as fully for all intents and purposes as he or she might or could do
in person, hereby ratifying and confirming all that said attorneys-in-fact and
agents, or their substitutes, may lawfully do or cause to be done by virtue
hereof.

     Pursuant to the requirements of the Securities Act of 1933, this
Registration Statement has been signed by the following persons in the
capacities indicated as of November 23, 1999.

<TABLE>
<CAPTION>
         Signature                                         Title                                      Date
         ---------                                         -----                                      ----
<S>                                         <C>                                                <C>
/s/ James R. Moxley, Jr.                    Chairman of the Board                              November 23, 1999
- ----------------------------
James R. Moxley, Jr.

/s/ John M. Bond, Jr.                       President and Chief Executive Officer              November 23, 1999
- ----------------------------                (Principal Executive Officer)
John M. Bond, Jr.

/s/ John A. Scaldara, Jr.                   Executive Vice President, Finance and              November 23, 1999
- ----------------------------
John A. Scaldara, Jr.

/s/ Herschel L. Langenthal                  Administration and Chief Financial Officer
- ----------------------------                (Principal Financial and Accounting Officer)
Herschel L. Langenthal

                                            Director                                           November 23, 1999
- ----------------------------
Anand S. Bhasin

/s/ Gannett Y. Clark, Jr.                   Director                                           November 23, 1999
- ----------------------------
Gannett Y. Clark, Jr.

/s/ Hugh F.Z. Cole, Jr.                     Director                                           November 23, 1999
- ----------------------------
Hugh F.Z. Cole, Jr.

                                            Director                                           November 23, 1999
- ----------------------------
G. William Floyd

/s/ William L. Hermann                      Director                                           November 23, 1999
- ----------------------------
William L. Hermann
</TABLE>
<PAGE>

<TABLE>
<S>                                         <C>                                                <C>
/s/ Charles C. Holman                       Director                                           November 23, 1999
- ----------------------------
Charles C. Holman

/s/ Harry L. Lundy, Jr.                     Director                                           November 23, 1999
- ----------------------------
Harry L. Lundy, Jr.

/s/ Richard E. McCready                     Director                                           November 23, 1999
- ----------------------------
Richard E. McCready

/s/ James R. Moxley III                     Director                                           November 23, 1999
- ----------------------------
James R. Moxley III

/s/ Mary S. Scrivener                       Director                                           November 23, 1999
- ----------------------------
Mary S. Scrivener

/s/ Maurice M. Simpkins                     Director                                           November 23, 1999
- ----------------------------
Maurice M. Simpkins

/s/ Robert N. Smelkinson                    Director                                           November 23, 1999
- ----------------------------
Robert N. Smelkinson

/s/ Theodore G. Venetoulis                  Director                                           November 23, 1999
- ----------------------------
Theodore G. Venetoulis

                                            Director                                           November 23, 1999
</TABLE>



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