EXHIBIT 23.1
POWER OF ATTORNEY
KNOW ALL MEN BY THESE PRESENTS, that each person whose signature appears below
constitutes and appoints Patrick B. Frost, Richard W. Evans, Jr. and Phillip D.
Green, and each of them, his true and lawful attorneys-in-fact and agents, and
with power of substitution and resubstitution, for him and in his name, place
and stead, and in any and all capacities, to sign the Annual Report on Form 10-K
of Cullen/Frost Bankers, Inc. for the fiscal year ended December 31, 2002, to
sign any and all amendments thereto, and to file such Annual Report and
amendments, with all exhibits thereto, and other documents in connection
therewith, with the Securities and Exchange Commission, granting unto said
attorneys-in-fact and agents, and each of them, full power and authority to do
and perform each and every act and thing requisite or necessary to be done in
and about the premises, as fully to all intents and purposes as he might or
could do in person, hereby ratifying and confirming all that said
attorneys-in-fact and agents or either of them, or their or his substitute or
substitutes, may lawfully do or cause to be done by virtue hereof.
<Table>
<Caption>
Signatures Title Date
- -------------------------------------- ----------------------------------- ----------------------
/s/ T.C. Frost Senior Chairman of the Board and March 27, 2003
- --------------------------------- Director
(T. C. Frost)
/s/ Richard W. Evans, Jr. Chairman of the Board March 27, 2003
- --------------------------------- and Director (Principal
(Richard W. Evans, Jr.) Executive Officer)
/s/ R. Denny Alexander Director March 27, 2003
- ---------------------------------
(R. Denny Alexander)
/s/ Carlos Alvarez Director March 27, 2003
- ---------------------------------
(Carlos Alvarez)
/s/ Isaac Arnold, Jr. Director March 27, 2003
- ---------------------------------
(Isaac Arnold, Jr.)
/s/ Royce S. Caldwell Director March 27, 2003
- ---------------------------------
(Royce S. Caldwell)
/s/ Harry H. Cullen Director March 27, 2003
- ---------------------------------
(Harry H. Cullen)
/s/ Eugene H. Dawson, Sr. Director March 27, 2003
- ---------------------------------
(Eugene H. Dawson, Sr.)
/s/ Ruben M. Escobedo Director March 27, 2003
- ---------------------------------
(Ruben M. Escobedo)
/s/ Patrick B. Frost Director March 27, 2003
- ---------------------------------
(Patrick B. Frost)
/s/ Joe R. Fulton Director March 27, 2003
- ---------------------------------
(Joe R. Fulton)
</Table>
<Table>
<Caption>
Signatures Title Date
- -------------------------------------- ----------------------------------- ----------------------
/s/ Preston M. Geren III Director March 27, 2003
- ---------------------------------
(Preston M. Geren III)
/s/ James L. Hayne Director March 27, 2003
- ---------------------------------
(James L. Hayne)
/s/ Karen E. Jennings Director March 27, 2003
- ---------------------------------
(Karen E. Jennings)
/s/ Richard M. Kleberg, III Director March 27, 2003
- ---------------------------------
(Richard M. Kleberg, III)
/s/ Robert S. McClane Director March 27, 2003
- ---------------------------------
(Robert S. McClane)
/s/ Ida Clement Steen Director March 27, 2003
- ---------------------------------
(Ida Clement Steen)
/s/ Horace Wilkins, Jr. Director March 27, 2003
- ---------------------------------
(Horace Wilkins, Jr.)
/s/ Mary Beth Williamson Director March 27, 2003
- ---------------------------------
(Mary Beth Williamson)
</Table>