InVO4 has aroused much interest because of its photo-catalytic property in the visible light range. Experimentally, it is hard to unravel the microscopic picture of InVO4 and the details of its electronic properties. We have thus performed first-principles band structure calculations of both the bulk and thin film of InVO4. The thin film was simulated by a surface slab model cleaved from the bulk and equilibrated via ab initio molecular dynamics simulations. We have compared the electronic structure properties with those of TiO2 that is the better known photo-catalyst. Our results show that the electronic structure of the InVO4 is quite sensitive to the atomic configuration of metal atoms around O, whereas that of TiO2 is not. In order to investigate the excitation levels, the quasiparticle energy structure of TiO2 has also been calculated via the GW (C) 2003 Elsevier Science B.V. All rights reserved.