<PAGE>

EXHIBIT 24.1


<PAGE>

                                POWER OF ATTORNEY

KNOW ALL MEN BY THESE PRESENTS:

         THAT I, Cecil D. Conlee, a director of Cornerstone Properties Inc. (the
"Company"), do hereby constitute and appoint John S. Moody, Kevin P. Mahoney and
Thomas P. Loftus, and each of them, my true and lawful attorneys-in-fact and
agents, to do any and all acts and things and to execute any and all instruments
which said attorney and agent may deem necessary or advisable to enable the
Company to comply with the Securities Exchange Act of 1934, as amended, and any
rules, regulations and requirements of the Securities and Exchange Commission in
respect thereof, in connection with the filing under the said Securities
Exchange Act of the Company's Annual Report on Form 10-K for the fiscal year
ended December 31, 1998 (the "Annual Report"), including specifically, but
without limiting the generality of the foregoing, the power and authority to
sign for, on behalf of and in the name of the undersigned as a director of the
Company, such Annual Report and any amendments thereto filed with the Securities
and Exchange Commission and any instrument or document filed as part of, an
exhibit to, or in connection with said Annual Report or amendments thereto; and
the undersigned does hereby ratify and confirm as his own act and deed all that
said attorneys-in-fact and agents shall do or cause to be done by virtue hereof.

         IN WITNESS WHEREOF, the undersigned has subscribed these presents,
effective as of the 22nd day of March, 1999.

                                             /s/ Cecil D. Conlee
                                             -------------------
                                             Cecil D. Conlee


<PAGE>

                                POWER OF ATTORNEY

KNOW ALL MEN BY THESE PRESENTS:

         THAT I, Blake Eagle, a director of Cornerstone Properties Inc. (the
"Company"), do hereby constitute and appoint John S. Moody, Kevin P. Mahoney and
Thomas P. Loftus, and each of them, my true and lawful attorneys-in-fact and
agents, to do any and all acts and things and to execute any and all instruments
which said attorney and agent may deem necessary or advisable to enable the
Company to comply with the Securities Exchange Act of 1934, as amended, and any
rules, regulations and requirements of the Securities and Exchange Commission in
respect thereof, in connection with the filing under the said Securities
Exchange Act of the Company's Annual Report on Form 10-K for the fiscal year
ended December 31, 1998 (the "Annual Report"), including specifically, but
without limiting the generality of the foregoing, the power and authority to
sign for, on behalf of and in the name of the undersigned as a director of the
Company, such Annual Report and any amendments thereto filed with the Securities
and Exchange Commission and any instrument or document filed as part of, an
exhibit to, or in connection with said Annual Report or amendments thereto; and
the undersigned does hereby ratify and confirm as his own act and deed all that
said attorneys-in-fact and agents shall do or cause to be done by virtue hereof.

         IN WITNESS WHEREOF, the undersigned has subscribed these presents,
effective as of the 22nd day of March, 1999.

                                             /s/ Blake Eagle
                                             ---------------
                                             Blake Eagle


<PAGE>

                                POWER OF ATTORNEY

KNOW ALL MEN BY THESE PRESENTS:

         THAT I, Hans C. Mautner, a director of Cornerstone Properties Inc. (the
"Company"), do hereby constitute and appoint John S. Moody, Kevin P. Mahoney and
Thomas P. Loftus, and each of them, my true and lawful attorneys-in-fact and
agents, to do any and all acts and things and to execute any and all instruments
which said attorney and agent may deem necessary or advisable to enable the
Company to comply with the Securities Exchange Act of 1934, as amended, and any
rules, regulations and requirements of the Securities and Exchange Commission in
respect thereof, in connection with the filing under the said Securities
Exchange Act of the Company's Annual Report on Form 10-K for the fiscal year
ended December 31, 1998 (the "Annual Report"), including specifically, but
without limiting the generality of the foregoing, the power and authority to
sign for, on behalf of and in the name of the undersigned as a director of the
Company, such Annual Report and any amendments thereto filed with the Securities
and Exchange Commission and any instrument or document filed as part of, an
exhibit to, or in connection with said Annual Report or amendments thereto; and
the undersigned does hereby ratify and confirm as his own act and deed all that
said attorneys-in-fact and agents shall do or cause to be done by virtue hereof.

         IN WITNESS WHEREOF, the undersigned has subscribed these presents,
effective as of the 22nd day of March, 1999.

                                             /s/ Hans C. Mautner
                                             -------------------
                                             Hans C. Mautner


<PAGE>

                                POWER OF ATTORNEY

KNOW ALL MEN BY THESE PRESENTS:

         THAT I, Lutz Mellinger, a director of Cornerstone Properties Inc. (the
"Company"), do hereby constitute and appoint John S. Moody, Kevin P. Mahoney and
Thomas P. Loftus, and each of them, my true and lawful attorneys-in-fact and
agents, to do any and all acts and things and to execute any and all instruments
which said attorney and agent may deem necessary or advisable to enable the
Company to comply with the Securities Exchange Act of 1934, as amended, and any
rules, regulations and requirements of the Securities and Exchange Commission in
respect thereof, in connection with the filing under the said Securities
Exchange Act of the Company's Annual Report on Form 10-K for the fiscal year
ended December 31, 1998 (the "Annual Report"), including specifically, but
without limiting the generality of the foregoing, the power and authority to
sign for, on behalf of and in the name of the undersigned as a director of the
Company, such Annual Report and any amendments thereto filed with the Securities
and Exchange Commission and any instrument or document filed as part of, an
exhibit to, or in connection with said Annual Report or amendments thereto; and
the undersigned does hereby ratify and confirm as his own act and deed all that
said attorneys-in-fact and agents shall do or cause to be done by virtue hereof.

         IN WITNESS WHEREOF, the undersigned has subscribed these presents,
effective as of the 22nd day of March, 1999.

                                             /s/ Lutz Mellinger
                                             ------------------
                                             Lutz Mellinger


<PAGE>

                                POWER OF ATTORNEY

KNOW ALL MEN BY THESE PRESENTS:

         THAT I, Craig R. Stapleton, a director of Cornerstone Properties Inc.
(the "Company"), do hereby constitute and appoint John S. Moody, Kevin P.
Mahoney and Thomas P. Loftus, and each of them, my true and lawful
attorneys-in-fact and agents, to do any and all acts and things and to execute
any and all instruments which said attorney and agent may deem necessary or
advisable to enable the Company to comply with the Securities Exchange Act of
1934, as amended, and any rules, regulations and requirements of the Securities
and Exchange Commission in respect thereof, in connection with the filing under
the said Securities Exchange Act of the Company's Annual Report on Form 10-K for
the fiscal year ended December 31, 1998 (the "Annual Report"), including
specifically, but without limiting the generality of the foregoing, the power
and authority to sign for, on behalf of and in the name of the undersigned as a
director of the Company, such Annual Report and any amendments thereto filed
with the Securities and Exchange Commission and any instrument or document filed
as part of, an exhibit to, or in connection with said Annual Report or
amendments thereto; and the undersigned does hereby ratify and confirm as his
own act and deed all that said attorneys-in-fact and agents shall do or cause to
be done by virtue hereof.

         IN WITNESS WHEREOF, the undersigned has subscribed these presents,
effective as of the 22nd day of March, 1999.

                                             /s/ Craig R. Stapleton
                                             ----------------------
                                             Craig R. Stapleton


<PAGE>

                                POWER OF ATTORNEY

KNOW ALL MEN BY THESE PRESENTS:

         THAT I, Donald G. Fisher, a director of Cornerstone Properties Inc.
(the "Company"), do hereby constitute and appoint John S. Moody, Kevin P.
Mahoney and Thomas P. Loftus, and each of them, my true and lawful
attorneys-in-fact and agents, to do any and all acts and things and to execute
any and all instruments which said attorney and agent may deem necessary or
advisable to enable the Company to comply with the Securities Exchange Act of
1934, as amended, and any rules, regulations and requirements of the Securities
and Exchange Commission in respect thereof, in connection with the filing under
the said Securities Exchange Act of the Company's Annual Report on Form 10-K for
the fiscal year ended December 31, 1998 (the "Annual Report"), including
specifically, but without limiting the generality of the foregoing, the power
and authority to sign for, on behalf of and in the name of the undersigned as a
director of the Company, such Annual Report and any amendments thereto filed
with the Securities and Exchange Commission and any instrument or document filed
as part of, an exhibit to, or in connection with said Annual Report or
amendments thereto; and the undersigned does hereby ratify and confirm as his
own act and deed all that said attorneys-in-fact and agents shall do or cause to
be done by virtue hereof.

         IN WITNESS WHEREOF, the undersigned has subscribed these presents,
effective as of the 22nd day of March, 1999.

                                             /s/ Donald G. Fisher
                                             --------------------
                                             Donald G. Fisher

<PAGE>

                                POWER OF ATTORNEY

KNOW ALL MEN BY THESE PRESENTS:

_________THAT I, Randall A. Hack, a director of Cornerstone Properties Inc. (the
"Company"), do hereby constitute and appoint John S. Moody, Kevin P. Mahoney and
Thomas P. Loftus, and each of them, my true and lawful attorneys-in-fact and
agents, to do any and all acts and things and to execute any and all instruments
which said attorney and agent may deem necessary or advisable to enable the
Company to comply with the Securities Exchange Act of 1934, as amended, and any
rules, regulations and requirements of the Securities and Exchange Commission in
respect thereof, in connection with the filing under the said Securities
Exchange Act of the Company's Annual Report on Form 10-K for the fiscal year
ended December 31, 1998 (the "Annual Report"), including specifically, but
without limiting the generality of the foregoing, the power and authority to
sign for, on behalf of and in the name of the undersigned as a director of the
Company, such Annual Report and any amendments thereto filed with the Securities
and Exchange Commission and any instrument or document filed as part of, an
exhibit to, or in connection with said Annual Report or amendments thereto; and
the undersigned does hereby ratify and confirm as his own act and deed all that
said attorneys-in-fact and agents shall do or cause to be done by virtue hereof.

_________IN WITNESS WHEREOF, the undersigned has subscribed these presents,
effective as of the 22nd day of March, 1999.


                                         /s/ Randall A. Hack
                                    ----------------------------------
                                             Randall A. Hack