Sol-gel SiO2-TiO2 mixed films have been deposited from a polymeric SiO2 solution and either a polymeric TiO2 mother solution (MS) or a derived TiO2 crystalline suspension (CS). The chemical and structural compositions of MS and CS mixed films heat-treated at 110 or 500 degrees C have been investigated by Fourier transform infrared spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. Water contact angle measurements show that TiO2 rich MS films exhibit photo-induced superhydrophilicity, but cannot maintain a zero contact angle in the absence of UV light. In contrast, CS mixed films exhibit a natural and persistent superhydrophilicity for a large range of compositions. Superhydrophilic properties are analyzed in terms of enhanced acidity at the SiO2-TiO2 interfaces and discussed with respect to the chemical and structural composition of MS and CS films.