The adsorption and oxidation reactions Of D-Mannitol at platinum single crystal electrodes with basal orientations have been studied by combining cyclic voltammetry and in situ FTIR spectroscopy. Cyclic voltammetric results have shown that, as far as current densities are concerned, the Pt(110) surface is the least active and more poisonable surface among the three platinum basal planes. The deactivation of Pt(100) and Pt(111) surfaces was found to be similar, although, higher current densities are obtained for Pt(100). FTIR spectroscopic experiments have indicated that CO is formed upon D-mannitol dissociative adsorption on the three basal platinum surfaces. This adsorbed intermediate, which was identified as the main poisoning species, is bonded to the platinum surface both in a linearly and bridge bonding mode and on a ratio which depends on the electrode surface orientation. The electro-oxidation process was found to be strongly dependent on the platinum crystalline surface structure. Moreover, additional voltammetric experiments performed on the three sets of platinum stepped surfaces have shown that the adsorption and oxidation reactions Of D-mannitol are sensitive to the symmetry of the bidimensional domains as well as to the distribution of orientated defects (monoatomic steps) on the platinum surfaces.