Benzophenone and some of its carboxylic acid derivatives were photoionized by a biphotonic process in aqueous solution. For all substances studied, the EPR spectra of the hydrated electrons e(aq)(-) and of radicals produced by the decay of the benzophenone radical cation could be detected on the nanosecond and microsecond time scale. Time-resolved optical measurements revealed additional reaction channels for the benzophenone radical cation decay. In general three different reaction channels were found, namely, the reaction of the radical cation with nucleophilic OH- under cyclohexadienyl radical formation, the generation of aryl radicals by beta-scission, and the generation of aryl radicals by CO2 elimination.