Supported copper particles are widely used in heterogeneous catalysis. Influence of supports of different nature on the Cu particles formation is studied by the methods of UV-Vis spectroscopy of diffuse reflectance, XRD and electron microscopy. Different states of supported copper have been identified by UV-Vis spectroscopy: absorption bands at 250 (Cu+), 320-370 and 400-440 (charge transfer bands of O-Cu-O and Cu-O-Cu complexes), 520-580 (Cu, plasmon resonance) and 620-850 nm (d-d transitions in Cu2+ ions). The size of Cu clusters and Cu-n/Cu-n(delta+) ratio strongly depends on the support nature. n (C) 2003 Elsevier B.V. All rights reserved.