A positive resist composition comprising (A) a resin component and (B) an acid generator component, wherein the component (A) is a copolymer which comprises constituent units (a1) derived from a mono(.alpha.-lower alkyl)acrylate having an acid-dissociable dissolution-inhibiting group, constituent units (b1) derived from a mono .alpha.-lower alkyl)acrylate having a lactone ring, and constituent units (c1) derived from a poly(.alpha.-lower alkyl)acrylate; and a positive resist composition comprising (A) a resin component and (B) an acid generator component, wherein the component (A) is a star polymer having a core containing acid-dissociable dissolution-inhibiting groups and arms bonded to the core.