We studied the deprotecting chemistry of poly(4-hydroxystyrene) based positive-working CA resist systems by using model reactions. Detailed analyses of acid-catalyzed deprotecting reactions of TMS-, THP-, and t-BOC-protected p-cresols were carried out, and it was found that alkylated derivatives of p- cresol were formed as major products for THP- and t-BOC-protected p-cresol, while no alkylated products were obtained for TMS derivatives after deprotection treatment (90 degree(s)C, 2 min). In the THP- and t-BOC-protected PHS systems were also observed such alkylations, which decreased the alkaline dissolution rate of the polymer film. The alkylations are considered to lower the alkaline dissolution contrast between an exposed area and an unexposed area in a resist film, and to deteriorate the resist performance. Therefore, we propose to introduce an alkylation inhibitor to the resist components so as to improve the performance.