Upon adsorption on Au(111) the symmetry is broken and the hydrogen atoms pointing towards the surface are repelled by steric repulsion. This causes the sp 3 carbons atoms to lie higher up (farther from the surface), a distortion that is still noticeable at the nearest sp 2 hybridized carbon atoms of the anthracene moiety and may even help in decoupling electronically the molecules from the substrate. This topographic effect translates into a larger STM signal at the higher C atoms and thus into the apparently stronger-than-expected contribution of the methyl groups to the frontier molecular orbitals.