TiO2 particles, rods, flowers and sheets were prepared by hydrothermal method via adjusting the temperature, the pressure and the concentration of TiCl4. The as-prepared TiO2 powders were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance spectra and N-2 adsorption-desorption measurements. It was found that pressure is the most important factor influencing the morphology of TiO2. The photocatalytic activity of the products was evaluated by the photodegradation of aqueous brilliant red X-3B solution under UV light. Among the as-prepared nanostructures, the flower-like TiO2 exhibited the highest photocatalytic activity. (c) 2007 Elsevier Ltd. All rights reserved.