-----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,
 KslS/ai340h1lMFIjAVu6fHmCHm5aslzl9HBNngSKG6Tc6cEj6MudQBiz/AkcQDb
 Rgt3FpsPZv1TYG/EV4JH4g==

<SEC-DOCUMENT>0001140361-07-000660.txt : 20070105
<SEC-HEADER>0001140361-07-000660.hdr.sgml : 20070105
<ACCEPTANCE-DATETIME>20070105130006
ACCESSION NUMBER:		0001140361-07-000660
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20070103
FILED AS OF DATE:		20070105
DATE AS OF CHANGE:		20070105

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			WHITWELL DAVID W
		CENTRAL INDEX KEY:			0001246225

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-27432
		FILM NUMBER:		07512718

	BUSINESS ADDRESS:	
		STREET 1:		C/O CLEAN DIESEL TECHNOLOGIES INC
		STREET 2:		300 ATLANTIC ST
		CITY:			STAMFORD
		STATE:			CT
		ZIP:			06901
		BUSINESS PHONE:		2033277050

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			CLEAN DIESEL TECHNOLOGIES INC
		CENTRAL INDEX KEY:			0000949428
		STANDARD INDUSTRIAL CLASSIFICATION:	INDUSTRIAL INORGANIC CHEMICALS [2810]
		IRS NUMBER:				061393453
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		300 ATLANTIC ST
		STREET 2:		STE 702
		CITY:			STAMFORD
		STATE:			CT
		ZIP:			06901
		BUSINESS PHONE:		2033277050

	MAIL ADDRESS:	
		STREET 1:		300 ATLANTIC ST
		STREET 2:		STE 702
		CITY:			STAMFORD
		STATE:			CT
		ZIP:			06901
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>doc1.xml
<DESCRIPTION>FORM 4
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2007-01-03</periodOfReport>

    <notSubjectToSection16>1</notSubjectToSection16>

    <issuer>
        <issuerCik>0000949428</issuerCik>
        <issuerName>CLEAN DIESEL TECHNOLOGIES INC</issuerName>
        <issuerTradingSymbol>CDTI</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001246225</rptOwnerCik>
            <rptOwnerName>WHITWELL DAVID W</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>5 MOHEGAN LANE</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>RYE BROOK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10573</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>1</isOther>
            <officerTitle></officerTitle>
            <otherText>Former Vice President &amp;  CFO</otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2007-01-03</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>D</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>12350</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>1.7774</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>12</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>David W. Whitwell</signatureName>
        <signatureDate>2007-01-05</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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