Ontologies　are　significant　for　the　development　of　the　semantic　web,　which　could　implement　the　information　reusing　and　knowledge　sharing.　With　the　number　of　ontologies　increasing　rapidly,　ontology　mapping　is　a　useful　method　to　clear　up　the　heterogeneity　among　ontologies　so　that　ontologies　could　understand　each　other　properly.　Structures　information　is　important　for　mining　semantic　relation　during　ontology　mapping.　In　the　ontology　hierarchy,　vertical　information　is　the　main　factor　used　in　many　mapping　methods,　while　the　horizontal　relation　is　not　employed　fully　yet.　In　this　paper,　from　the　aspect　of　the　dimensions　of　the　concept　in　ontologies,　which　describes　the　horizontal　relation　of　ontology　concepts,　an　ontology　mapping　approach　is　proposed.　The　values　on　concept　dimensions　could　be　named　concepts,　intersections,　unions,　complements　or　restrictions.　They　are　compared　with　ontology　concepts　to　help　ontology　mapping.　Experiments　indicate　that　the　concept　dimension　is　an　important　factor　infecting　ontology　mapping.　©　2009　IEEE.