Zinc oxide films were made by spray pyrolysis equipped with an optical system for in situ thickness measurement. Films were fabricated from zinc acetate water solution. The solution's pH was modified to increase film porosity, which was subsequently analyzed using scanning electron microscopy. X-ray diffractometry revealed that resulting films were zincite-like with a preferred (0 0 2) direction depending on the temperature of deposition. Spectral optical equipment analyzed the absorption of ZnO based films in the 350-800 nm. The various zinc oxide films were brought in contact with methyl orange, whose photo-electrocatalytically induced degradation under ultraviolet irradiation was investigated in a reactor allowing optical probing of methyl orange. Results can be reconciled with the active area's suitability for producing photoinduced holes capable of effecting oxidation of the pollutant. © 2002 Elsevier Science B.V. All rights reserved.