A positive resist composition comprises (A) a resin component which becomes soluble in an alkaline developer under the action of an acid and (B) an acid generator. The resin (A) is a polymer comprising specific recurring units, represented by formula (1). The acid generator (B) is a specific sulfonium salt compound. When processed by lithography, the composition is improved in resolution and forms a pattern with a satisfactory mask fidelity and a minimal LER. Herein R1 is H or methyl, R2 is an acid labile group, R3 is CO2R4 when X is CH2, R3 is H or CO2R4 when X is O, R4 is a monovalent C1-C20 hydrocarbon group, and m is 1 or 2.