A three-dimensional, single phase, isothermal model is developed to predict the high frequency resistance (HFR) variation with time during dry air purge of a polymer electrolyte fuel cell (PEFC) with straight channels. For the first time, an investigation of HFR characteristics of a PEFC following the purge is carried out. Predicted membrane water content during and after the purge is used to calculate the HFR from known membrane ionic conductivity relations. Only cathode purge is considered as typical in the industry to minimize waste of hydrogen. Results show that the governing factor of water distribution in the membrane during purge is through plane and in-plane concentration gradient and HFR relaxation is mainly governed by concentration differential between inlet and outlet.