Density　functional　theory　(DFT)　calculations　are　used　to　characterize　the　doping　effect　of　N　substitution　of　O　in　hexagonal　In2O3　and　N　occupying　vacant　anion　site　of　cubic　In2O3.　The　results　show　that　in　both　N-doped　systems　localized　N　2p　states　are　principally　formed　above　the　top　of　the　O　2p　valence　band,　leading　to　the　reduction　of　the　photon　transition　energy,　and　the　redshifts　of　the　absorption　edge.　When　the　doping　level　rises,　the　energy　gap　has　little　further　narrowing　compared　with　that　at　lower　doping　concentrations,　and　the　larger　formation　energies　are　required　for　the　synthesis　of　two　polymorphs　N-doped　In2O3.　(C)　2008　Elsevier　B.V.　All　rights　reserved.