We have investigated the effect of flow field patterns without cathode humidification in a polymer electrolyte fuel cell (PEFC) using electrochemical impedance spectroscopy (EIS) with triple-parallel-serpentine, interdig-itated, and serpentine-interdigitated hybrid flow fields. The hybrid flow fields exhibit better performance than the others. The EIS results indicate that dehydration of the membrane and catalyst layer (CL) is significant for the triple-parallel-serpentine flow fields whereas that for the hybrid flow fields is not so severe. Thus the serpentine-interdigitated hybrid flow field has advantage in cell operation without cathode humidification, possibly because it provides a relatively uniform current distribution due to the in-terdigitated flow channel, and in addition, the serpentine flow channel involved in the hybrid flow field supplies water vapor along the channel. This water distribution behavior is also indicated by ex-situ tracer distribution observation using gas diffusion layers sprayed with water soluble metal salt tracer at the CL side.