The electronic structure of thin blend films composed of copper phthalocyanine (CuPc) and fulierene (C-60) have been studied by x ray, soft-x-ray photoemission spectroscopy, and by theoretical simulations. Samples with different C-60/CUPC concentration ratios were prepared by thermal evaporation in ultrahigh vacuum conditions. A strong shift of the highest occupied molecular orbital (HOMO) of CuPc towards the Fermi level and of the HOMO C-60 states towards higher binding energy was observed. The comparison between valence band structures and core level line shape indicates that the central part of the CuPc molecule is lightly modified by the presence of the C-60 molecule. The theoretical analysis, performed using density functional theory, confirms this small interaction between the two molecules, with a small charge density localized between the two molecules and a structural modification of the CuPc molecule. (c) 2006 American Vacuum Society.