Decahedral anatase titanium(IV) oxide (TiO2) with {1 0 1} and {0 0 1} exposed crystal faces was prepared by hydrothermal treatment of peroxo titanic acid (PTA) solution with polyvinyl alcohol (PVA) as a shape-control reagent. pH of the PTA solution and amounts of PVA and amorphous titania included in the PTA solution had a large influence on size and shape of the prepared particles, and particle width of the decahedral anatase TiO2 was controllable between 25 and 60 nm. Photocatalytic activity of the decahedral anatase TiO2 was examined in terms of the relationship between particle size and photocatalytic activity. Decahedral anatase TiO2 with particle width of ca. 40 nm showed excellent activity because of the optimized balance between efficient separation of redox sites and large specific surface area. (C) 2012 Elsevier B.V. All rights reserved.