The adsorbed residue originating from the contact of sulfur dioxide with smooth platinum electrodes is characterized by both in situ FTIR and cyclic voltammetry in 1 M HF solution. It is found that the adsorbed layer is composed partially by adsorbed elemental sulfur and molecular SO2. FTIR data show a potential dependent spectral feature ranging between 980 and 1020 cm(-1), which could be assigned to SO2 molecules adsorbed either through a pyramidal geometry with one-fold coordination under a C-s symmetry, or through a bridge-bonded geometry under C-2v symmetry. Electrochemical determination of the electrons per site required to oxidize the previously reduced adsorbed layer suggests that both coordinations should exist for potentials in the double layer region of the platinum electrode. No spectral feature is observed for potentials in the hydrogen region and the electrons per site indicate that the adsorbate is of the type Pt-S-2.