<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2004-11-03</periodOfReport>

    <notSubjectToSection16>1</notSubjectToSection16>

    <issuer>
        <issuerCik>0000720195</issuerCik>
        <issuerName>LIFELINE SYSTEMS INC</issuerName>
        <issuerTradingSymbol>LIFE</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001129787</rptOwnerCik>
            <rptOwnerName>VA PARTNERS LLC</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>435 PACIFIC AVENUE</rptOwnerStreet1>
            <rptOwnerStreet2>FOURTH FLOOR</rptOwnerStreet2>
            <rptOwnerCity>SAN FRANCISCO</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>94133</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001159187</rptOwnerCik>
            <rptOwnerName>UBBEN JEFFREY W</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>435 PACIFIC AVENUE, FOURTH FLOOR</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>SAN FRANCISCO</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>94133</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0000937541</rptOwnerCik>
            <rptOwnerName>KAMIN PETER H</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>TWO INTERNATIONAL PLACE, 25TH FLOOR</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>BOSTON</rptOwnerCity>
            <rptOwnerState>MA</rptOwnerState>
            <rptOwnerZipCode>02110</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2004-11-03</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>2127400</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>22.7</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>0</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See Footnote</value>
                    <footnoteId id="F1"/>
                    <footnoteId id="F2"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">As General Partner and Investment Manager of ValueAct Capital Master Fund, L.P.
and ValueAct Capital Partners Co-Investors, L.P.</footnote>
        <footnote id="F2">These securities were beneficially owned by Jeffrey W. Ubben, George F. Hamel, Jr., and Peter H. Kamin as Managing Members, Principal Owners and Controlling Persons of VA Partners, LLC. The reporting persons disclaim beneficial ownership except to the extent of their pecuniary interest therein.</footnote>
    </footnotes>

    <remarks>Joint Filer Information

Name: ValueAct Capital Master Fund, L.P.
Address: 435 Pacific Avenue, Fourth Floor, San Francisco, CA 94133
Designated Filer: VA Partners, L.L.C.
Issuer and Ticker Symbol: Lifeline Systems, Inc. (LIFE)
Statement for Month/Day/Year: November 3, 2004

Name: ValueAct Capital Partners Co-Investors, L.P.
Address: 435 Pacific Avenue, Fourth Floor, San Francisco, CA 94133
Designated Filer: VA Partners, L.L.C.
Issuer and Ticker Symbol: Lifeline Systems, Inc. (LIFE)
Statement for Month/Day/Year: November 3, 2004

Name: Jeffrey W. Ubben
Address: 435 Pacific Avenue, Fourth Floor, San Francisco, CA 94133
Designated Filer: VA Partners, L.L.C.
Issuer and Ticker Symbol: Lifeline Systems, Inc. (LIFE)
Statement for Month/Day/Year: November 3, 2004

Name: George F. Hamel, Jr.
Address: 435 Pacific Avenue, Fourth Floor, San Francisco, CA 94133
Designated Filer: VA Partners, L.L.C.
Issuer and Ticker Symbol: Lifeline Systems, Inc. (LIFE)
Statement for Month/Day/Year: November 3, 2004

Name: Peter H. Kamin
Address: 435 Pacific Avenue, Fourth Floor, San Francisco, CA 94133
Designated Filer: VA Partners, L.L.C.
Issuer and Ticker Symbol: Lifeline Systems, Inc. (LIFE)
Statement for Month/Day/Year: November 3, 2004</remarks>

    <ownerSignature>
        <signatureName>VALUEACT CAPITAL MASTER FUND, L.P., BY VA PARTNERS, L.L.C., ITS GENERAL PARTNER By: /s/ George F. Hamel, Jr. Managing Member</signatureName>
        <signatureDate>2004-11-05</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>VALUEACT CAPITAL PARTNERS CO-INVESTORS, L.P., BY VA PARTNERS, L.L.C., ITS GENERAL PARTNER By: /s/ George F. Hamel, Jr. Managing Member</signatureName>
        <signatureDate>2004-11-05</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>VA PARTNERS, L.L.C. By: /s/ George F. Hamel, Jr. Managing Member</signatureName>
        <signatureDate>2004-11-05</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>By: /s/ Jeffrey W. Ubben</signatureName>
        <signatureDate>2004-11-05</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>By: /s/ George F. Hamel, Jr.</signatureName>
        <signatureDate>2004-11-05</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>By: /s/ Peter H. Kamin</signatureName>
        <signatureDate>2004-11-05</signatureDate>
    </ownerSignature>
</ownershipDocument>

