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We study the photolytic degradation of planar (PCB 2, PCB 12, PCB 13, PCB 15) and non-planar (PCB 8, PCB 29, PCB 31) polychlorobiphenyls in an aqueous alcohol under UV irradiation (=240-320nm) at ambient temperature and atmospheric pressure for 25h on nanocrystalline TiO2 and CdS/TiO2. It is found that a conversion of PCB 2 (12.5%), PCB 12 (42.3%) and PCB 29 (98.0%) is more intense in the presence of the CdS/TiO2 composite, whereas mixture of the congeners PCB 8, PCB 13, PCB 15 and the congener PCB 31 can be photolyzed better in the presence of TiO2 with conversion 35.2% and 96.1%, respectively. The different conversions of the PCB congeners are explained considering the structures of the chloroaromatic radicals formed in situ as a result of the primary photolysis process and are confirmed by means of estimation of dipole moments calculated for singlet states of PCBs.