Understanding losses in polymer electrolyte membrane fuel cells, in the form of ohmic and mass transport, is of great importance to their commercialization. In this study, we use a spatially resolved cell consisting of 49 segments to measure the local current density distribution and high frequency resistance (HFR). A parametric study is used to investigate the effects of cell voltage, inlet relative humidity and flow rate and configuration using a three-channel serpentine flow field. We found that as the cell voltage decreased, the current density increased, while the HFR decreased. However, at a low cell voltage of 200 mV, we found the HFR to be higher than that at 500 mV. This increase is attributed to the increased electro-osmotic drag. This trend is independent of the flow configuration. Further, we found that the effect of the inlet relative humidity on the HFR highly depends on the flow configurations. Finally, a sharp decrease in the current density at some specific bend segments was observed, which correlates with lower OCV values and higher HFR values at this position. Copyright (C) 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.