Elementary processes of motions of single adsorbed molecules on metal surfaces induced by inelastic tunneling currents with scanning tunneling microscope are discussed in conjunction with novel experimental results. A coherent multiple-step vibrational ladder climbing following a direct excitation of the reaction coordinate (RC) mode, or an indirect excitation of the RC mode through the anharmonic coupling to the high-frequency mode excited by tunneling electrons, to overcome the potential barrier along the RC associated with the relevant motions are combined to gain a deep insight into how competing different reaction pathways can be selectively activated within a single adsorbed molecule. (C) 2004 Elsevier B.V. All rights reserved.