The substitution reaction of aromatic nuclei, such as N,N-dialkylated aromatic amines and methoxy-substituted arenes with perfluoroalkyl R_f groups was acomplished in water by a photoinduced method to yield the substitution products resulting from replacement of aromatic H’s with the R_f moiety in good yields (57-88%). Mechanistic aspects are discussed giving support for a photoinduced electron transfer substitution (PET) reaction. A radical chain mechanism superimposed with a redox process is proposed to account for product formation, as evidenced by the observation of the UV-vis transient spectra of the radical cation species generated from electron-rich aromatic compounds in the presence of perfluoroalkyl halides by Nanosecond Laser Flash Photolysis (NLFP) techniques.