Exhibit 1.1
 EXECUTION VERSION
 2,725,000 Shares
 CLEAN DIESEL TECHNOLOGIES, INC.
 Common Stock
 UNDERWRITING AGREEMENT
   
 
  Company Schedule I Underwriters Underwritten Shares Common Stock Schedule II Selling Stockholders Selling Stockholder Secondary Shares Additional Shares Shares Representative
  1. Registration Statement and Prospectus Commission Securities Act Rules and Regulations




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Registration Statement Rule 462 Registration Statement Preliminary Prospectus Pricing Prospectus
 Final Prospectus Prospectus
 EDGAR Exchange Act
 2. Representations and Warranties of the Company Regarding the Offering.
    2




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Marketing Materials
   Time of Sale Disclosure Package Schedule III
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Issuer Free Writing Prospectus
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3. Representations and Warranties Regarding the Company.
  Material Adverse Effect
   5




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Contracts
     6




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taxes returns
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Permits
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9




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Intellectual Property
  OFAC
     10




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11




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4. Representations and Warranties of the Selling Stockholders.
        12




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5. Purchase, Sale and Delivery of Shares.
 Per Share Price
  13




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Option Notice Option Closing Date provided however
  Closing Date
 6. Covenants.
  Prospectus Delivery Period
  14




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15




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Company Expenses
  16




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Schedule IV
   Schedule III Permitted Free Writing
Prospectus
 Lock-Up Period
  17




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Registration Rights Agreement
     18




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provided
    7. Conditions of the Underwriters Obligations.
   19




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Schedule V
 Schedule VI.
     20




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Schedule VII
    21




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8. Indemnification and Contribution
 provided, however
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provided however
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Schedule I
   9. Representations and Agreements to Survive Delivery
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10. Termination of this Agreement
   11. Notices th
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12. Persons Entitled to Benefit of Agreement
 13. Absence of Fiduciary Relationship
 14. Amendments and Waivers
 15. Partial Unenforceability
 16. Governing Law
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17. Submission to Jurisdiction
 18. Counterparts.
  28




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Very truly yours,COMPANY:
CLEAN DIESEL TECHNOLOGIES, INC.By:
    /s/ Nikhil A. MehtaName:
    Nikhil A. MehtaTitle:
    Chief Financial OfficerSELLING STOCKHOLDERS:
ROCKPORT CAPITAL PARTNERS, L.P.By:
    RockPort Capital I, LLC, its General PartnerBy:
    /s/ Janet B. JamesName:
    Janet B. JamesTitle:
    Managing MemberRP CO-INVESTMENT FUND I, L.P.By:
    RP Co-Investment Fund I GP, LLC, its General PartnerBy:
    /s/ Janet B. JamesName:
    Janet B. JamesTitle:
    Managing Member Confirmed as of the date first
above-mentioned by the Underwriters.ROTH CAPITAL PARTNERS, LLC
Acting as Representative of the Underwriters
named in Schedule IBy:
    
    /s/ Aaron M. Gurewitz

Name: Aaron M. GurewitzTitle:   Head of Equity Markets




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SCHEDULE I
 Number of
    
    
    Number ofUnderwritten
    
    
    Secondary
    
    
    Number ofShares to be
    
    
    Shares to be
    
    
    Additional SharesPurchased
    
    
    Purchased
    
    
    to be PurchasedUnderwritersRoth Capital Partners, LLC
    
    
    2,512,750
    
    
    
    76,000
    
    
    
    388,313Maxim Group LLC
    
    
    132,250
    
    
    
    4,000
    
    
    
    20,437Total
    
    
    2,645,000
    
    
    
    80,000
    
    
    
    408,750




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SCHEDULE II
 Number ofUnderwritten and
    
    
    Number ofSecondary Shares
    
    
    Additional Sharesto be Sold
    
    
    to be SoldCompany:Clean Diesel Technologies, Inc.
    
    
    2,645,000
    
    
    
    408,750Selling Stockholders:RockPort Capital Partners, L.P.
    
    
    72,800
    
    
    
    RP Co-Investment Fund I, L.P.
    
    
    7,200
    
    
    
    Total
    
    
    2,725,000
    
    
    
    408,750




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SCHEDULE III
 Issuer:
    
    Clean Diesel Technologies, Inc. (the Company)Symbol:
    
    CDTISecurity:
    
    Common stock, par value $0.01 per shareCompany Shares:
    
    2,645,000 shares of common stockSelling Stockholders Shares:
    
    80,000 shares of common stockOver-allotment option:
    
    408,750 additional shares of common stockPublic offering price:
    
    $3.75 per shareUnderwriting discounts and
commissions:
    
    $0.2292 per shareNet proceeds (excluding the
over-allotment):
    
    $8.7 million (after deducting the
underwriters discounts and commissions and
estimated offering expenses payable by the
Company)Trade date:
    
    June 29, 2011Settlement date:
    
    July 5, 2011Underwriters:
    
    Roth Capital Partners, LLC
Maxim Group LLC




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SCHEDULE IV
 Warrant




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SCHEDULE V
 Company Opinions




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SCHEDULE VI
 Selling Stockholders Opinions




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SCHEDULE VII
 Lockups