Hydrolysis of 4-acetoxystyrene polymers prepared by atom transfer radical polymerization was carried out under various reaction conditions. It was found that hydrazinolysis of 4-acetoxystyrene homopolymers, random and block copolymers with styrene in 1,4-dioxane, afforded the corresponding narrow dispersed materials with phenolic groups which were substantially free from crosslinkages. Gel permeation chromatographic (GPC) analysis of these polymers revealed different extents of molecular weight distribution (MWD) broadening for the hydrolysis products for the different structures. On the other hand, by NaOH catalyzed deprotection, the 4-acetoxystyrene polymers including triblock copolymer poly(4-acetoxystyrene-b-isobutylene-b-4-toxystyrene) suffered from some degrees of coupling or even gelation, except for poly(styrene-b-4-acetoxystyrene-b-styrene) which also by this method could be conveniently converted to its phenolic product.