We present the results of ab initio calculations describing the adsorption of certain small organic molecules on clean and oxidized Al(111) surfaces as well as on the α- Al₂O₃(0001) surface. Our results show that adsorption of benzene on the clean and oxidized Al(111) surfaces is generally weak, the adsorption energy being at most around −0.5 eV per benzene molecule, and the molecule adsorbed at a considerable distance from the surfaces. The adsorption energy varies weakly at the different adsorption sites and as a function of the oxygen coverage. For the alumina surface, we find no benzene adsorption at all. We have also calculated for a phenol molecule on the aluminum and alumina surfaces, since it is similar to the benzene molecule. The results show a weak adsorption for phenol on the alumina surface and no adsorption on the aluminum or oxidized aluminum surfaces at all. For the propane molecule there is no adsorption on either the oxidized aluminum or the alumina surface, whereas the carbonic acid molecule binds strongly to the alumina but not to the aluminum surface.