Photocatalytic properties of TiO2 aqueous suspension were analyzed by means of the chemiluminescent probe method, which enables us to monitor superoxide ions (O-.(2)-) and hydrogen peroxide (H2O2) in the reaction system. The amount of produced O-.(2)- is independent of the surface properties of TiO2, while H2O2 is formed significantly for smaller particles with large amount of surface hydroxyl groups. The amount of produced (OH)-O-. radicals was estimated from the effect of Cl- ions on the O-.(2)- formation and found to be large for the TiO2 having a large amount of surface hydroxyl groups. This difference is explained to originate from the different structure of hole intermediates, based on the ESR measurements for these powders at 77 K.