A quantum study of the sticking of hydrogen and deuterium atoms chemisorbed onto graphite (0001) surface is carried out in the collinear scattering approximation, taking into account the phonon modes of the system. The sticking coefficients are calculated for hydrogen and deuterium atoms with incident energies ranging from 0.17 to 0.22 eV, for surface temperatures of 10 and 150 K. The calculation of the sticking coefficients of H and D evidenced an isotopic effect which is discussed. (C) 2009 Elsevier B.V. All rights reserved.