Several carbon blacks and graphite were investigated as candidates for diffusion layer preparation in polymer electrolyte fuel cell electrodes (PEFC). Single cell electrochemical characterizations under different working cell conditions were carried out on the electrodes by varying the kind of carbon in the diffusion layer. An improvement in cell performance was found by using Shawinigan Acetylene Black (SAB) as carbon, resulting in a measured power density of about 360 mW cm(-2) in H-2/air operation at 70 degreesC and 1/1 bar. Pore size distribution and scanning electron microscopy analyses were carried out to help the understanding of the different behaviour of the investigated carbon diffusion layers.