The effect of the alpha-CD coating on the electronic states and electric conduction of molecular wires was investigated with the help of the first-principles calculation and Green's function method. When molecules were coated with alpha-CD, the energy of molecular orbitals was stabilized and the molecular structure changed due to the steric hindrance although the HOMO-LUMO gap did not change. As a consequence, alpha-CD coating reduced the electronic transmission and electric conductance. (c) 2006 Elsevier B.V. All rights reserved.