POWER OF ATTORNEY

Know all by these presents, that the undersigned, as a Section 16
reporting person of Cowen Group, Inc. (the "Company") hereby
constitutes and appoints each of Owen S. Littman and Stephen A.
Lasota, or either of them signing singly, and with full power of
substitution, the undersigned's true and lawful attorney-in-fact
to:

(1) prepare, execute in the undersigned's name and on the
undersigned's behalf, and submit to the U.S. Securities and
Exchange Commission (the "SEC") a Form ID, including amendments
thereto, and any other documents necessary or appropriate to
obtain codes and passwords enabling the undersigned to make
electronic filings with the SEC of reports required by Section
16(a) of the Securities Exchange Act of 1934 (the "Exchange Act")
or any rule or regulation of the SEC;

(2) execute for and on behalf of the undersigned, as a Section 16
reporting person of the Company, Forms 3, 4 and 5 in accordance
with Section 16(a) of the Exchange Act and the rules thereunder,
and any other forms or reports the undersigned may be required to
file in connection with the undersigned's ownership, acquisition,
or disposition of securities in the Company;

(3)do and perform any and all acts for and on behalf of the
undersigned which may be necessary or desirable to complete and
execute any such Form 3, 4 or 5, or other form or report, and
timely file such form with the SEC and any stock exchange or
similar authority; and

(4)take any other action of any type whatsoever in connection with
the foregoing which, in the opinion of such attorney-in-fact, may
be of benefit to, in the best interest of, or legally required by,
the undersigned, it being understood that the documents executed
by such attorney-in-fact on behalf of the undersigned pursuant to
this Power of Attorney shall be in such form and shall contain
such terms and conditions as such attorney-in-fact may approve in
such attorney-in-fact's discretion.

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 attorneys-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 Power of Attorney shall remain in full force and effect until
the undersigned is no longer required to file Forms 3, 4 and 5
with respect to the undersigned's holdings of and transactions in
securities issued by the Company, unless earlier revoked by the
undersigned in a signed writing delivered to the foregoing
attorneys-in-fact.

IN WITNESS WHEREOF, the undersigned has caused this Power of
Attorney to be executed as of this 7th day of November, 2012.

/s/ Katherine Elizabeth Dietze
Katherine Elizabeth Dietze