EXHIBIT 23.3
CONSENT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM
We consent to the incorporation by reference in this Registration Statement on Form S-3 of our reports dated February 27, 2015, relating to the consolidated financial statements of Columbia Banking System Inc., and the effectiveness of Columbia Banking System, Inc.’s internal control over financial reporting, appearing in the Annual Report on Form 10-K of Columbia Banking System, Inc. for the year ended December 31, 2014, and to the reference to us under the heading “Experts” in the Prospectus, which is part of this Registration Statement.
/S/ DELOITTE & TOUCHE LLP
Seattle, WA
August 5, 2015
