The　HCNH　and　CNH2　adsorption　on　different　coordination　sites　of　Cu(100)　was　theoretically　studied　considering　the　cluster　approach.　The　present　calculations　show　that　the　bridge　site　is　the　most　favorite　for　CNH2　perpendicularly　adsorbed　on　the　Cu(100)　surface　via　the　C　atom.　For　HCNH　absorbed　on　the　Cu(100)　surface,　the　parallel　adsorption　mode　with　the　C　and　N　atoms　nearly　directly　above　the　adjacent　top　sites　of　Cu(100)　surface　is　the　most　favored.　Both　CNH2　and　HCNH　are　strongly　bound　to　the　Cu(100)　surface　with　CNH2　Which　is　lightly　stable　(2.51　kJ　center　dot　mol(-1)),　indicating　that　both　species　may　be　co-adsorbed　on　the　Cu(100)　surface.