TiO2-based nanostructures usually possess excellent photochemical properties. However, the relationship between their dimensionality and photocatalytic activity was rarely investigated. In this study, a series of TiO2-based nanostructures in various dimensionalities (such as nanosheets, nanotubes) were obtained by hydrothermal treatment of P25, and the process of structural evolution was also systematically investigated by TEM, BET, Raman, and XRD analysis. Much higher rate constant (3.7 x 10(-2) min(-1)) for the degradation of rhodamine B was found for nanosheets, comparing with those of three-dimensional P25 nanoparticles (0.59 x 10(-2) min(-1)) and one-dimensional nanotubes (0.85 x 10(-2) min(-1)). It is found that the hydrothermally prepared TiO2-based nanosheets possess small thickness (ca. 5 nm) and plentiful surface hydroxyl groups, and the reason why TiO2-based nanosheets possess superior photocatalytic activity is also discussed in detail from the microstructure and surface chemical states. In addition, TiO2-based nanosheets exhibit good reusability in the cyclic experiments, implying a potential application for photocatalytic degradation of organic pollutants.