Press Release


Columbia Banking System to Present at RBC Capital Markets 2005 Financial Institutions Conference

Company Release - 9/15/2005 1:37 PM ET

TACOMA, Wash., Sept. 15 /PRNewswire-FirstCall/ -- Columbia Banking System, Inc. (Nasdaq: COLB) today announced that Melanie J. Dressel, President and Chief Executive Officer and Gary R. Schminkey, Executive Vice President and Chief Financial Officer, will present the Company's financial performance and business strategies at RBC Capital Markets' Financial Institutions Conference on Wednesday, September 21, 2005. The presentation will begin at 11:30 a.m. EDT (8:30 a.m. PDT) and may be accessed live over the internet through the webcast link: http://www.wsw.com/webcast/rbc33/colb. An archived webcast of the presentation will be available through the same link for approximately 30 days after the conference.

Columbia Banking System, Inc. is a Tacoma-based bank holding company whose wholly owned bank subsidiaries are Columbia Bank and Bank of Astoria, which was acquired October 1, 2004. Columbia Bank is a Washington state-chartered full-service commercial bank with 36 banking offices in Pierce, King, Cowlitz, Kitsap and Thurston counties. Bank of Astoria, a federally insured commercial bank headquartered in Astoria, Oregon, operates four branches in Clatsop County: Astoria, Warrenton, Seaside and Cannon Beach; and one branch in Manzanita in Tillamook County.

    Contacts: Melanie J. Dressel, President and
              Chief Executive Officer
              (253) 305-1911
              Gary R. Schminkey, Executive Vice President
              and Chief Financial Officer
              (253) 305-1966
              JoAnne Coy, Vice President, Marketing Director
              253-305-1965


SOURCE  Columbia Banking System, Inc.
    -0-                             09/15/2005
    /CONTACT:  Melanie J. Dressel, President and Chief Executive Officer,
+1-253-305-1911, Gary R. Schminkey, Executive Vice President and Chief
Financial Officer, +1-253-305-1966, or JoAnne Coy, Vice President, Marketing
Director, +1-253-305-1965, all of Columbia Banking System, Inc./
    /Web site:  http://www.columbiabank.com /
    (COLB)

CO:  Columbia Banking System, Inc.
ST:  Washington
IN:  FIN
SU:  TDS CCA

JO
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3271 09/15/200513:37 EDThttp://www.prnewswire.com