In the present study TiO2 has been supported on several rigid substrates. Deposition on glass and quartz was carried out by a dip coating procedure and the deposition on stainless steel by an electrophoretic deposition process. The resulting materials have been characterized by XPS, SEM/EDX, XRD and UV-vis absorption spectroscopy. The materials were then tested for the photocatalytic degradation of malic acid. For this reaction, the sample supported on quartz showed the highest catalytic activity. The photocatalytic activity pattern as a function of the nature of the support (fused silica, glass, stainless steel) followed the decreasing order : TiO2/quartz> TiO2/steel approximate to TiO2/glass much greater than photolysis. This decline in activity has been correlated with the presence of cationic impurities (Si4+, Na+, CP3+, Fe3+) in the layer as a consequence of the necessary thermal treatments to improve the cohesion of the titania layer and its adhesion onto the support.