The photocatalytic activity of titanium oxide supported on ZSM5, zeolite A, silica, and alumina was investigated using the photooxidation of 4-chlorophenol and acetophenone as test reactions. It was found that the photocatalytic activity of titanium oxide on ZSM5 and zeolite A was higher than that of a TiO2 powder prepared in parallel or TiO2 formed on silica and alumina, respectively. TiO2/ZSM5, which showed the highest photoactivity at low Ti content, was observed to have large adsorptivity for the organic substrates. It was also found that a decrease in zeolite crystallinity decreased the photoactivity of TiO2/zeolite A. These observations suggest that adsorption and zeolite structure are factors which may be responsible for enhancement of photocatalytic activity of supported TiO2. The sample characterization by XRD, BET, FTIR, and Raman spectroscopy indicates that titanium oxide is formed as small particles of anatase on all the supports and that there are also noncrystalline titanium oxide species farmed on zeolite supports. Maximal photocatalytic activity is observed at low (<2%) titanium oxide loading on ZSM5.