A method for performing neutron radiography and locally resolved impedance spectroscopy simultaneously in Situ in all operating polymer electrolyte fuel cell (PEFC) is presented. The new method provides Concurrently spatially resolved information about the local cell performance, the locally limiting processes, and the liquid water distribution. Information about the impact of water oil cell performance and limiting processes call be gained in situ oil a local scale in all operating PEFC. The method was applied to a PEFC operated oil pure H-2/O-2 in co-flow mode under low humidity operating conditions. The results show that in co-flow mode strong flooding and severe drying can Occur at the very same time in different sections of a PEFC.