We show that, counterintuitively, maleic anhydride on Si(1 0 0) surfaces adsorbs on inter-row sites, Our first principles simulations establish that this site is preferred for coverages of less than 1/8 ML, In simulations of scanning tunnelling images we establish also, that the corrugation is enhanced by more than 0.5 Angstrom, if a single molecular state contributes to the tunnelling current. The combined evidence of images and simulations allows the conclusion that experiments in fact reveal the geometry of single molecular wavefunctions. (C) 2002 Published by Elsevier Science B.V.