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,　CuCUS,　and　Lewis　base　site,　OSUF　are　considered　for　adsorption.　Adsorption　energies　and　the　energies　of　the　dissociation　reaction　N2O　→　N2　+　O(s)　at　different　sites　are　calculated.　The　calculations　show　that　adsorption　of　N2O　is　more　favorable　on　CuCUS　adsorption　site　energetically.　CuCUS　site　exhibits　a　very　high　activity.　The　CuCUS-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　OSUF-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.　©　2007　Elsevier　B.V.　All　rights　reserved.