Geometric pore surface area is a significant parameter for the description of the irregular, somewhat random, porous structure of the catalyzed electrodes in polymer electrolyte membrane (PEM) fuel cells; however, its value is sensitive to the experimental methods employed, which necessitates the measurements via different methods. In this study, the geometric surface area of the porous electrode is determined by two different methods: the method of standard porosimetry (MSP) and Brunauer-Emmett-Teller (BET). The theory of fractal dimension is employed to analyze the data obtained from the MSP, and the fractal surface area calculated using nitrogen molecules as the scale is compared with the BET surface area. The results indicate that the geometric pore surface area is a property of the porous electrode that depends greatly on the "scale" size (ie, molecule size of the working fluid)-a smaller scale yields a larger value of the surface area. The surface area determined by the BET is found to be about one order of magnitude larger than that obtained by the MSP. Thus, the fractal dimension theory based on MSP demonstrates a useful tool to determine the accessible pore surface area at different length scales.