C-80 cages with encapsulated group III and lanthanide nitrides are systematically studied through density functional calculation. Most intercalated fullerenes M3N@C-80 exhibit similar spectroscopic features near Fermi level, in consistent with experimental results. We establish that the plane of Sc3N is perpendicular to the C-5 axis, rather than the C-3 axis as proposed before. The charge transfer from metal atoms toward N and C atoms is quantitatively analyzed. The role of 4f states treated as valence states is explored through LSDA + U calculation finally. (C) 2008 Elsevier B.V. All rights reserved.