Size-quantized TiO2 particles immobilized in polyvinylpyrrolidinone (Q-TiO2/PVPD) films, were prepared by electrophoretic deposition of Q-TiO2 colloids in 2-propanol in the presence of PVPD as a stabilizing agent. The Q-TiO2 prepared had the average diameter of 3.3 nm with a standard,deviation of 1.1 nm. Illumination of the Q-TiO2/PVPD film in water-free 2-propanol resulted in the production of acetone as a sole oxidation product and Ti3+ species as the reduction product, and when the Ti3+ species was accumulated, hydrogen evolution began to occur. The same was true for bulk TiO2 particles immobilized in the same matrix, which were prepared by soaking the Q-TiO2/PVPD film in water, but the rate of these photoinduced reactions was much slower than that of the Q-TiO2. The photoformation of Ti3+ in the TiO2 particles was suppressed by introduction of NO3- to 2-propanol, suggesting that the formation of the Ti3+ species is controlled by kinetics of electron transfer to accepters in solution.