In this study, we investigated vacuum-treated TiO2 nanocrystals. They displayed long-wavelength optical absorption due to the existence of oxygen vacancy and Ti3+ defects, and also possibly the surface structural disorder. Both oxygen vacancy and Ti3+ defects influenced the photocatalytic activities in methylene blue decomposition and hydrogen generation. Oxygen vacancy benefited photocatalytic methylene blue (MB) decomposition, but harmed the photocatalytic hydrogen generation. Ti3+ defects displayed a more complicated effect. (C) 2013 Elsevier B.V. All rights reserved.