A method for a rough estimation of the catalyst surface area in a fuel cell is developed. It is based on the deconvolution of experimental CO oxidation data by use of a mathematical model. The kinetic parameters of the model are determined by fitting the experimental curves. The experimental data are collected at different sweep rates (2-100 mV s(-1)) and at different temperatures (room -60.0 A degrees C). The model can predict the sweep rate dependence of the CO oxidation onset potential, the peak current, the peak potential and the peak broadness. The model is further used for the prediction of the baseline in the presence of CO and for calculation of the CO charge consumed up to half peak potential. It is obtained that the latter value is constant at different sweep rates and that the baseline deviates from linearity already at low sweep rates (2 mV s(-1)), but not very significantly (2.0% in comparison to 8.8% at 100 mV s(-1), based on calculated CO charge). It is suggested that lower sweep rates should be used for experimental surface area determination.