In the present study, two different designs of flow field have been evaluated by electrochemical impedance spectroscopy for polymer electrolyte membrane fuel cells. Ex-situ experiments were conducted in serpentine and interdigitated flow field geometry. We have investigated the serpentine type flow field designs with varying rib and channel width geometry and studied their influence on the PEMFC performance. The anodic and cathodic resistances were also evaluated using symmetrical mode of operation. The three different types of multichannel serpentine geometry with 2,1 and 0.7 mm rib and channel widths were used for evaluation and found that the mass transfer resistance was decreasing with rib& channel width thickness. The mass transfer resistance decreased by one order from 0.197 Omega for 2 mm channel width to 0.016 Omega for 0.7 mm channel width. The maximum power density obtained for PEMFC operating on H-2/Air at 50 degrees C, with 0.7, 1&2 mm rib and channel width was found to be 365, 291 and 202 mW/cm(2) respectively. This study emphasized the effect of rib and channel width geometry of flow fields by symmetrical mode of fuel cell operation using electrochemical impedance spectroscopy to obtain the anodic and cathodic mass transfer resistance individually. (C) 2012 Elsevier Ltd. All rights reserved.