The photocatalytic hydrogen production over TiO2 nanoparticles with mesostructures has been studied using CH3OH as a sacrificial reagent. The effects of the calcination temperature, Pt-loading, amount of TiO2 and methanol as well as irradiation time on the H-2 evolution rate were investigated in detail. The results indicated that the as-synthesized TiO2 nanoparticles without calcination, having a large specific surface area (438 m(2)/g) and small crystallite size (2.3 nm) dispersed among the amorphous mesoporous domains, exhibited the best photocatalytic activity for H2 production compared with the samples calcined at different temperatures and the commercial photocatalyst P25 (Degussa, Germany) under the same photoreaction conditions. The presence of mesostructured TiO2 nanoparticles with a uniform dispersion of the co-catalyst (Pt) has resulted in an effective, faster charge separation, which, in turn, leads to a higher photocatalytic activity for H2 production. (C) 2007 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.