The Source Function (SF) atomic contributions were evaluated at bond critical points (bcps) for three test systems, using theoretical electron densities and multipole modelled densities derived from the former projected into structure factors. In general, the SF percentage atomic contributions obtained from the multipole modelled density agree well with those calculated from the corresponding primary density, despite large discrepancies in the electron density and, particularly, in the density Laplacian values occur at bcps. The SF percentage contributions represent a more robust chemical bond descriptor than are other commonly used bond topological indices which are too sensitive to the multipole model bias. (C) 2009 Elsevier B.V. All rights reserved.