We applied the two-color resonant two-photon mass-analyzed threshold ionization spectroscopic technique to record the cation spectra of o-fluoroanisole and p-fluoroanisole. The adiabatic ionization energies of these two structural isomers were found to be 67354 +/- 5 and 66437 +/- 5 cm(-1), respectively. The observed active normal modes of the cations mainly result from the in-plane ring and substituent-sensitive vibrations. The results suggest that the relative location of the F and OCH3 substituents can slightly influence the transition energy and molecular vibrations. (C) 2012 Elsevier B. V. All rights reserved.