The voltammetric behaviour of Pt-TiO2 coated stainless steel electrodes, prepared by the MOCVD procedure, was investigated in both concentrated and diluted acid aqueous solutions. The composition of the nanocomposites was in the Pt:Ti range 1:10 to 1:80 atomic ratio. The composition effect on the hydrogen evolution reaction was investigated to get insights on both the activity of the platinum particles present in the composites as well as their spatial distribution. To this latter aim, a series of measurements was also carried out using the Scanning Electrochemical Microscopy (SECM) technique. The results obtained showed that even small amounts of platinum in the composites provide some activity towards the hydrogen evolution reaction. It however proved the higher, the larger was the Pt content in the matrix. The Pt distribution in the various composites revealed anyway uniform across the surface, regardless of the Pt:Ti atomic ratios. The results obtained in solutions containing acids were compared with those obtained in Ru(NH3)(6)CI3.