Gas-phase photocatalytic oxidation of hexane over nanosized TiO2 catalysts with different specific surface area, particle size and crystal phase at ambient temperature was studied and compared with Degussa P25. The photo-oxidation products are CO2 and H2O, and the activity is dominantly dependent on the surface area of the catalysts, although the faster electron-hole recombination in smaller TiO2 particles exerts to a certain extent a negative effect on the photocatalytic process. No significant difference in the activity has been observed between pure anatase and rutile catalysts with comparable specific surface area and particle size. Sulfation of anatase TiO2 catalysts improves their activity and stability efficiently. The complete oxidation of methanol and benzene to CO2 and H2O can also be achieved on the sulfated nanosized anatase photocatalysts successfully, and the catalysts are rather stable after reaching the steady state.