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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,
 Av0Y9tRqzAVnslL5yTcbodey7X2qsGyOKW0QOR+UETuKw+vrT1cmcsnaoWLhUsbr
 UANisTfN1GzwwZlfObFswA==

<SEC-DOCUMENT>0001181478-06-000022.txt : 20060306
<SEC-HEADER>0001181478-06-000022.hdr.sgml : 20060306
<ACCEPTANCE-DATETIME>20060306135140
ACCESSION NUMBER:		0001181478-06-000022
CONFORMED SUBMISSION TYPE:	3
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20060227
FILED AS OF DATE:		20060306
DATE AS OF CHANGE:		20060306

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			CADENCE DESIGN SYSTEMS INC
		CENTRAL INDEX KEY:			0000813672
		STANDARD INDUSTRIAL CLASSIFICATION:	SERVICES-PREPACKAGED SOFTWARE [7372]
		IRS NUMBER:				770148231
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			0102

	BUSINESS ADDRESS:	
		STREET 1:		2655 SEELY ROAD BLDG 5
		CITY:			SAN JOSE
		STATE:			CA
		ZIP:			95134
		BUSINESS PHONE:		4089431234

	MAIL ADDRESS:	
		STREET 1:		555 RIVER OAKS PARKWAY
		CITY:			SAN JOSE
		STATE:			CA
		ZIP:			95134

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	ECAD INC /DE/
		DATE OF NAME CHANGE:	19880609

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Swainson John A
		CENTRAL INDEX KEY:			0001309401

	FILING VALUES:
		FORM TYPE:		3
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-10606
		FILM NUMBER:		06666735

	BUSINESS ADDRESS:	
		BUSINESS PHONE:		631-342-2168

	MAIL ADDRESS:	
		STREET 1:		C/O COMPUTER ASSOCIATES INTL., INC.
		STREET 2:		ONE COMPUTER ASSOCIATES PLAZA
		CITY:			ISLANDIA
		STATE:			NY
		ZIP:			11746
</SEC-HEADER>
<DOCUMENT>
<TYPE>3
<SEQUENCE>1
<FILENAME>edgar.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>3</documentType>

    <periodOfReport>2006-02-27</periodOfReport>

    <noSecuritiesOwned>0</noSecuritiesOwned>

    <issuer>
        <issuerCik>0000813672</issuerCik>
        <issuerName>CADENCE DESIGN SYSTEMS INC</issuerName>
        <issuerTradingSymbol>CDNS</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001309401</rptOwnerCik>
            <rptOwnerName>Swainson John A</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>2655 SEELY AVENUE, BLDG. 5</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>SAN JOSE</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>95134</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>0</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <footnotes></footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>R.L. Smith McKeithen, Attorney-in-Fact for John A. C. Swainson</signatureName>
        <signatureDate>2006-03-06</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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