Density　functional　theory　has　been　employed　to　investigate　the　adsorption　and　the　dissociation　of　an　N2O　at　different　sites　on　perfect　and　defective　Cu2O(1　1　1)　surfaces.　The　calculations　are　performed　on　periodic　systems　using　slab　model.　The　Lewis　acid　site,　Cu-CUS,　and　Lewis　base　site,　O-SUF　are　considered　for　adsorption.　Adsorption　energies　and　the　energies　of　the　dissociation　reaction　N2O　-＞　N-2　+　O(s)　at　different　sites　are　calculated.　The　calculations　show　that　adsorption　of　N2O　is　more　favorable　on　Cu-CUS　adsorption　site　energetically.　Cu-CUS　site　exhibits　a　very　high　activity.　The　Cu-CUS-N2O　reaction　is　exothermic　with　a　reaction　energy　of　77.45　kJ　mol(-　1)　and　an　activation　energy　of　88.82　kJ　mol(-1),　whereas　the　O-SUF-N2O　reaction　is　endothermic　with　a　reaction　energy　of　205.21　kJ　mol(-1)　and　an　activation　energy　of　256.19　kJ　mol(-1).　The　calculations　for　defective　surface　indicate　that　O　vacancy　cannot　obviously　improve　the　catalytic　activity　Of　Cu2O.　(c)　2007　Elsevier　B.V.　All　rights　reserved.