-----BEGIN PRIVACY-ENHANCED MESSAGE-----
Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
Originator-Key-Asymmetric:
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 TWSM7vrzLADbmYQaionwg5sDW3P6oaM5D3tdezXMm7z1T+B+twIDAQAB
MIC-Info: RSA-MD5,RSA,
 CgUOklmODPZ9z3brNJlgOwIs96ayQ6iUtTOS8R7yIAZwpe3u6FJuGp1jobUYZ9/M
 TjIyYgpPSOJSZmAt7mBEfg==

<SEC-DOCUMENT>0001202458-08-000005.txt : 20080702
<SEC-HEADER>0001202458-08-000005.hdr.sgml : 20080702
<ACCEPTANCE-DATETIME>20080702173327
ACCESSION NUMBER:		0001202458-08-000005
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20080630
FILED AS OF DATE:		20080702
DATE AS OF CHANGE:		20080702

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			NELSON MARK W
		CENTRAL INDEX KEY:			0001202458

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-20288
		FILM NUMBER:		08935654

	BUSINESS ADDRESS:	
		STREET 1:		1301 A STREET
		CITY:			TACOMA
		STATE:			WA
		ZIP:			98402-4200

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			COLUMBIA BANKING SYSTEM INC
		CENTRAL INDEX KEY:			0000887343
		STANDARD INDUSTRIAL CLASSIFICATION:	STATE COMMERCIAL BANKS [6022]
		IRS NUMBER:				911422237
		STATE OF INCORPORATION:			WA
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		1102 BROADWAY PLAZA
		CITY:			TACOMA
		STATE:			WA
		ZIP:			98402
		BUSINESS PHONE:		2533051900

	MAIL ADDRESS:	
		STREET 1:		1102 BROADWAY PLAZA
		CITY:			TACOMA
		STATE:			WA
		ZIP:			98402
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>edgar.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0303</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2008-06-30</periodOfReport>

    <issuer>
        <issuerCik>0000887343</issuerCik>
        <issuerName>COLUMBIA BANKING SYSTEM INC</issuerName>
        <issuerTradingSymbol>COLB</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001202458</rptOwnerCik>
            <rptOwnerName>NELSON MARK W</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>1301 A STREET, STE. 800</rptOwnerStreet1>
            <rptOwnerStreet2>MS-3100</rptOwnerStreet2>
            <rptOwnerCity>TACOMA</rptOwnerCity>
            <rptOwnerState>WA</rptOwnerState>
            <rptOwnerZipCode>98402-4200</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Executive Vice President</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2008-06-30</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>446</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>17.397</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>21958</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Non-Qualified Stock Option (Right to Buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>10.68</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2008-03-03</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>M</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>10500</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <value>2005-10-23</value>
            </exerciseDate>
            <expirationDate>
                <value>2010-10-23</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Non-Qualified Stock Option</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>0</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>0</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">This was an ESPP purchase.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>Cathleen Dent</signatureName>
        <signatureDate>2008-07-02</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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