We studied the scanning tunneling microscope-induced luminescence (STML) of conjugated polymer poly[2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylene vinylene (MEH-PPV) spun from the solutions with various concentrations on metal substrates Ag and Au. Characteristic molecular fluorescence with the intrinsic molecular vibronic peaks associated with the HOMO-LUMO transition appears in addition to the curve based on plasmon-mediated light emission from the metal substrate Ag or Au. We found that it is a necessary condition to observe molecular fluorescence that the plasmon-mediated light from the metal substrate, which depends on the substrate, is intense in the absorption band of the molecule. (C) 2007 Elsevier B.V. All rights reserved.