An AM1 (restricted Hartree-Fock) type semiempirical quantum chemical study has been performed on certain series of Se containing fused ring systems, which possess a Se atom in a five-membered ring system at beta-position to a keto group. The substituents are at any of peri-positions of the adjacent aromatic ring such that, due to the topology of the system, the substituent in one case are nearby the Se atom and in the other case nearby the C=O group. The study shows that all the systems are to be stable. Generally, the structures of the first type are more stable than their isomeric compounds of second type. Some other quantum chemical properties of these systems beside their energetics have been reported. (C) 2004 Elsevier B.V. All rights reserved.