Photodeposition followed by postheating under different conditions yielded Pt particles on TiO2, in a highly dispersed state with a mean size (d) ranging from 1.1 to 9.2 nm (Pt/TiO2). Adsorption experiments of elemental sulfur (S-8) on Pt/TiO2 showed that S is almost selectively adsorbed on the Pt surfaces independently of d (S-Pt/TiO2) and that the amount of S adsorbed per unit Pt surface area increases as the d value increases. Light irradiation (lambda(ex) > 300 nm) to S-Pt/TiO2 in water led to S-desorption, of which rate increases with increasing d in the size range.