Solvation effect on the electronic structure of small molecules is examined using a combination of the RISM-SCF and an analysis, in which resonance structures and their weights are extracted from ab initio molecular orbitals. The present method provides us chemical intuitions on solvation effect from modern quantum computational results. The illustrative results on hydrogen halides and water molecules in an aqueous solution are presented. (c) 2006 Elsevier B.V. All rights reserved.