We present six-dimensional quantum dynamics calculations oil scattering of (r = 0, j = 0) H-2 and D-2 from Cu(1 1 1), at normal incidence. Theoretical results for dissociative chemisorption and vibrationally inelastic scattering. which were obtained using two different LEPS potential energy surfaces. are compared to experiment. The theoretical probabilities for vibrational excitation are too low by about an order of magnitude. The luck of competition with vibrational excitation leads to reaction probabilities which are probably too high at large collision energies, These discrepancies are related to the LEPS PESs used in the calculations and possible improvements are discussed. (C) 2002 Elsevier Science B.V. All rights reserved.