hexafluorobenzene in the presence of benzophenone resulted in both, substitution and addition products. Similar photoreaction has been observed by irradiation of hexafluorobenzene in some alcohols in the presence of benzophenone. The reaction of pentafluorobenzene with methanol or cyclohexane resulted in the substitution of a 2-or 4-fluoro atom, while the reaction of pentafluoroanisole resulted in the formation of