We present an experimental and theoretical study of He, Ne and Ar diffraction from the Ru (0001) surface. Close-coupling calculations were performed to estimate the corrugation function and the potential well depth in the atom–surface interaction in all three cases. DFT (density functional theory) calculations, including van der Waals dispersion forces, were used to validate the close-coupling results and to further analyze the experimental results. Our DFT calculations indicate that, in the incident energy range 20–150 meV, anticorrugating effects are present in the case of He and Ar diffraction, whereas normal corrugation is observed with Ne beams.