The present paper concerns the development of a polymer electrolyte membrane (PEM) fuel cells model in order to analyse the behaviour of the cell varying its operating parameters such as temperature (70-120 degrees C), pressure (1-3 atm), relative humidity (35-100%) and CO content (0-200 ppm) in the feeding gas. The voltage output and the relative current of a generic PEM fuel cell has been predicted through a mathematical method based on semi-empirical correlations derived from the experimental data available in literature. The model has been implemented in a commercial process simulator (AspenPlus) and it has been validated by comparing the obtained results with further experimental data (not utilized for the model development). The comparison has underlined a good agreement with the experimental behaviour of the fuel cell showing the reliability of the model. Copyright (C) 2010, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.