High resistance films of the anatase phase of TiO2 have been prepared by spray pyrolysis starting with titanium isopropoxide Ti(OPr(i))4. The films were deposited on glass substrates held at 590 K. The TiO2 films were characterized structurally, optically, and electrically. The photoresponse of these films to prolonged UV radiation in a vacuum and subsequently subjected to O2, H-2, water vapour, or air environments, has been investigated. When vacuum, O2 or air is present, the electrical and optoelectronic properties observed can be explained by the induced variations in the oxygen deficiency at the surface of the TiO2 film and the resulting formation or removal of an enhancement layer at the surface. An equivalent effect on the surface band bending can be induced by an adsorbed species. For example, adsorbed water vapour can alter the surface conductance of the films and the result depends on the oxygen-to-titanium ratio present at the surface when the water vapour is introduced.