The non-dissociative adsorption energy of a series of alcohols over a rutile Ti 8O 29H 26 cluster, representing the TiO 2(0 1 1) surface, as well as over a rutile Ti 11O 42H 40 cluster, representing the TiO 2(1 1 0) surface, was computed by means of a semi-empirical PM3 method. Over TiO 2(0 1 1) surface the non-dissociative adsorption energy of methanol, ethanol, n-propanol and i-propanol were 1.29, 1.46, 2.08, and 2.40 eV, respectively. This trend can reasonably be explained by gas phase acidity, as measured by their relative (to methanol) polarizability. On the other hand, the same series investigated over TiO 2(1 1 0) gave the following adsorption energy values: 1.49, 1.60, 1.96, and 1.94 eV, respectively. The relatively low adsorption energy for i-propanol, shows a deviation from the expected correlation. The reason for that is most likely structural. While TiO 2(1 1 0) surface contains Ti 4+ cations five- and six-fold coordinated to oxygen, TiO 2(0 1 1) surface contains Ti 4+ all in a five-fold coordination environment. Thus, it appears that the alternating rows of bridging oxygen anions of the (1 1 0) surface exert a repulsive interaction over the two-methyl groups of i-propanol decreasing its adsorption energy.