The formation of reduced CO2 was investigated on Pt(110)-(1 x 2), Pt(100) and Pt(111) in sulfuric acid solution by anodic stripping voltammetry (ASV) after potentiostatic adsorption at different adsorption potentials and periods. The order of catalytic activity of CO2 reduction was found to be Pt(110) > Pt(100) > Pt(111); maximum charge amount of oxidation of reduced CO2 formed at 0.10 V (vs. rhe) seems to be ca. 300 muC cm-2 on Pt(110) but ca. 90 muC cm-2 on Pt(100). The reduced CO2 at Pt(100) was found to locate on terrace sites but not on edge sites. Assignment of reduced CO2 species by ratio of the amount of charge of reduced CO2 oxidation to the amount of charge decrease of the adsorbed hydrogen is discussed.