In contrast to the common view, living cationic polymerization of p-methoxy- and p-t-butoxystyrenes proceeded in polar solvents such as EtNO2/CH2Cl2 mixtures, and involvement of free ionic growing species therein was examined. For example, the two alkoxystyrenes were polymerized with the isobutyl vinyl ether-HCl adduct/ZnCl2 initiating system at -15 degrees C in such polar solvents as CH2Cl2 or EtNO2/CH2Cl2 [1/1 (v/v)], as well as toluene. The number average molecular weight ((M) over bar)(n) of the polymers increased in direct proportion to the monomer conversion, even after sequential monomer addition, and the molecular weight distribution (MWD) stayed very narrow throughout the reaction. In addition, the (M) over bar(n) agreed with the calculated values, assuming that one adduct molecule generates one living polymer chain. In these polar media the addition of a common ion salt retarded the polymerization, indicating that dissociated ionic species are involved in the propagating reaction.