Abstract: Gas diffusion layers (GDL) in proton exchange membrane fuel cells were prepared by graphitization of polyacrylonitrile carbon fiber cloths, to enhance their properties, such as, electrical conductivity, which was examined by electrical tests, X-ray diffraction, and elemental analysis. The results indicated that electrical resistivity declined, Lc increased, and d002 decreased with an increase in the heat-treatment temperature. Carbon fiber cloths with a higher heatª²treatment temperature performed better as GDLs in terms of current density and power density.