<SUBMISSION>
<ACCESSION-NUMBER>0001246360-09-001391
<TYPE>4
<PUBLIC-DOCUMENT-COUNT>2
<PERIOD>20090401
<FILING-DATE>20090402
<DATE-OF-FILING-DATE-CHANGE>20090402
<REPORTING-OWNER>
<OWNER-DATA>
<CONFORMED-NAME>SIBONI ROGER S
<CIK>0001105624
<STATE-OF-INCORPORATION>DE
<FISCAL-YEAR-END>1231
</OWNER-DATA>
<FILING-VALUES>
<FORM-TYPE>4
<ACT>34
<FILE-NUMBER>001-10606
<FILM-NUMBER>09729541
</FILING-VALUES>
<MAIL-ADDRESS>
<STREET1>1900 SOUTH NORFOLK STREET
<CITY>SAN MATEO
<STATE>CA
<ZIP>94403
</MAIL-ADDRESS>
</REPORTING-OWNER>
<ISSUER>
<COMPANY-DATA>
<CONFORMED-NAME>CADENCE DESIGN SYSTEMS INC
<CIK>0000813672
<ASSIGNED-SIC>7372
<IRS-NUMBER>770148231
<STATE-OF-INCORPORATION>DE
<FISCAL-YEAR-END>1229
</COMPANY-DATA>
<BUSINESS-ADDRESS>
<STREET1>2655 SEELY ROAD BLDG 5
<CITY>SAN JOSE
<STATE>CA
<ZIP>95134
<PHONE>4089431234
</BUSINESS-ADDRESS>
<MAIL-ADDRESS>
<STREET1>555 RIVER OAKS PARKWAY
<CITY>SAN JOSE
<STATE>CA
<ZIP>95134
</MAIL-ADDRESS>
<FORMER-COMPANY>
<FORMER-CONFORMED-NAME>ECAD INC /DE/
<DATE-CHANGED>19880609
</FORMER-COMPANY>
</ISSUER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>form.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0303</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2009-04-01</periodOfReport>

    <notSubjectToSection16>false</notSubjectToSection16>

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001105624</rptOwnerCik>
            <rptOwnerName>SIBONI ROGER S</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>true</isDirector>
            <isOfficer>false</isOfficer>
            <isTenPercentOwner>false</isTenPercentOwner>
            <isOther>false</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Non-qualified stock option (right to buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>4.06</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2009-04-01</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>false</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>25000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <value>2010-03-31</value>
            </exerciseDate>
            <expirationDate>
                <value>2019-04-01</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>25000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>25000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <ownerSignature>
        <signatureName>James J. Cowie, Attorney-in-Fact for Roger S. Siboni</signatureName>
        <signatureDate>2009-04-02</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
<DOCUMENT>
<TYPE>EX-24
<SEQUENCE>2
<FILENAME>poasiboni.txt
<TEXT>
POWER OF ATTORNEY



I, Roger S. Siboni, hereby authorize Michael J. Fister, William Porter,
James J. Cowie or Kevin Palatnik of Cadence Design Systems, Inc.,
a Delaware corporation
(the Company), to sign and file on my behalf the Initial Statement of
Beneficial Ownership of Securities on Form 3, Statements of Changes in
Beneficial Ownership on Forms 4 and 5, and any Amendments and applications
thereto, to be filed with the Securities and Exchange Commission pursuant to
Section 16(a) of the Securities Act of 1934 relating to my beneficial
ownership of securities in the Company. The undersigned hereby grants
to each such attorney-in-fact full power and authority to do and perform
any and every act and thing whatsoever requisite, necessary, or proper
to be done in the exercise of any of the rights and powers herein granted,
as fully to all intents and purposes as the undersigned might or
could do if personally present, with full power of substitution or
revocation, hereby ratifying and confirming all that such
attorney-in-fact, or such attorney-in-fact s substitute or substitutes,
shall lawfully do or cause to be done by virtue of this power of
attorney and the rights and powers herein
granted.  The undersigned acknowledges that the foregoing
attorney-in-fact, in serving in such capacity at the request of the
undersigned, are not assuming, nor is the Company assuming, any of the
undersigned s responsibilities to comply with Section 16 of the Securities
Exchange Act of 1934. This authorization shall remain in effect until I am
no longer required to file forms under Section 16(a) with respect to the
Company s securities, unless earlier revoked in writing delivered to
the foregoing attorneys-in-fact.


/s/ Roger S. Siboni				April 7, 2008
Roger S. Siboni                                      Date


</TEXT>
</DOCUMENT>
</SUBMISSION>
