A number of applications of titanium dioxide including air and water cleaning rely on photocatalytic activity of its anatase form while others making use of UV-shielding and reflectivity properties employ rather the rutile form. Here we compare photoelectrochemical activity of TiO2 films formed from nanocrystalline anatase and rutile particles of similar sizes and shapes. Particularly high incident photon-to-current conversion efficiencies observed for the oxidation of organic molecules at the anatase films contrast with the poor activity of the nanostructured rutile films. (C) 2009 Elsevier Ltd. All rights reserved.