The cationic polymerization of cyclohexene oxide (CHO), n-butyl vinylether (BVE), N-vinylcarbazole (NVC), and 4-vinyl cyclohexenedioxide (4-VCHD) is initiated upon UV irradiation (lambda(inc.) = 350 nm) of dichloromethane solution containing N-ethoxy-2-methyl-pyridinium hexafluorophosphate (EMP(+)PF(6)) and o-phthaldehyde. A feasible initiation mechanism involves formation of biradical by intramolecular hydrogen abstraction of triplet o-phthaldehyde. Oxidation of these radicals by EMP(+) ions yields protons capable of initiating the cationic polymerization.