Thin boron-doped diamond films have been prepared by HF CVD (hot filament chemical vapour deposition technique) on conductive p-Si substrate (Si/Diamond). The morphology of these Si/diamond electrodes has been investigated by SEM and Raman spectroscopy. The electrochemical behaviour of the Si/diamond electrodes in 1 M H2SO4 and in 1 M H2SO4 + carboxylic acids has been investigated by cyclic voltammetry. Finally, the electrochemical oxidation of some simple carboxylic acids (acetic, formic, oxalic) has been investigated by bulk electrolysis. These acids can be oxidized at Si/diamond anodes to CO2, in the potential region of water and/or the supporting electrolyte decomposition, with high current efficiency.