Photocatalytically active TiO2 thin-films were deposited on silicon wafers using the Successive-Ionic-Layer-Adsorption-and-Reaction technique and subsequent hydrothermal and/or furnace annealing. Atomic-force-microscopy images and X-ray diffraction measurements of the TiO2 films obtained under various annealing conditions show how changes of the micro-scale surface structure depend on the post-SILAR treatment. The hydrogen evolution over various TiO2 films was measured. Hydrothermally treated TiO2 films show a higher photocatalytic activity and a much better mechanical stability compared to furnace-annealed films. The optical transmittance of TiO2 thin films on glass substrates was also studied. A red shift was observed with increasing film thickness. TiO2 nanoparticles (similar to 10 nm) that were peeled off from the TiO2 films were investigated using high-resolution-transmission-electron-microscopy. (c) 2006 Published by Elsevier B.V.