CdS-TiO2 thin film heterojunctions were prepared on glass and indium, tin oxide (ITO) substrates with the aim of improving photocatalytic efficiency both in UV-visible and visible light irradiation. The CdS under-layers were prepared by chemical bath deposition technique and subsequently they were annealed in the high vacuum of 5 x 10(-5) Pa at the temperature of 400 degrees C. The structural and optical properties of all the CdS-TiO2 thin films were studied with the help of X-ray diffractometer, atomic force microscope and ultraviolet-visible spectrophotometer. The photocatalytic activity of the thin films was evaluated by the decomposition of methanol by the use of fourier transform infrared spectrophotometer. It is revealed that the use of ITO substrate and high-vacuum annealing after deposition significantly enhance photocatalytic activity. (c) 2008 Elsevier B.V All rights reserved.