The energetic and electronic properties of F and/or Zr-doped anatase TiO2 are investigated by first-principles calculations. For F-doping, reduced Ti3+ ions are formed and Ti orbitals lie slightly below the conduction band, leading to band gap narrowing. For Zr-doping, Zr 4d orbitals reside well into the conduction band, with essentially no band gap change. For F/Zr-codoping, the electronic structure is similar to that for F-monodoping, where Ti3+ gap states are induced by both the oxygen vacancy and F dopant. The influence of oxygen vacancies indicates that interplay between dopants and oxygen vacancies is key for improvement of photocatalytic activity. The theoretical findings present a reasonable explanation of recent experimental results. (C) 2010 Elsevier B.V. All rights reserved.