An electrochemical model for H2 oxidation and O2 reduction in HT-PEM fuel cells derived from multi-step single electron transfer elementary reactions is presented. The exchange current density expressions are free from arbitrary order dependency with respect to the concentration of reactants and products. The reaction mechanism also considers CO adsorption and desorption, which enables the prediction of cell performance drop due to CO poisoning. The electrochemical model is coupled with a quasi two dimensional model of the cell, which resolves the flow channel in the axial direction and the electrodes along its length and thickness. A 3 cm long cell is simulated and the results are compared with experimental measurements. Very good agreement is obtained between the model predictions and experimental measurements for cell operating on pure H2 and with 1–16% CO in the temperature range of 150–200 °C. © 2017 Elsevier Ltd