Synchrotron X-ray radiography was utilized to visualize the liquid water distribution in a fuel cell with an active area of 0.48 cm(2) with an effective spatial resolution of 10 mu m. Water content was measured in the gas diffusion layers (GDLs), where microporous layer (MPL) thicknesses ranged between 0 and 150 mu m. The distribution of liquid water in a substrate-free polymer electrolyte membrane (PEM) fuel cell with a 50 mu m-thick MPL was also determined. It was observed that the presence of an MPL significantly reduced the water content at the interfacial region between the catalyst layer and GDL, and increasing the thickness of the MPL led to a reduction of liquid water accumulation at the interface between the substrate and MPL. (C) The Author(s) 2015. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives 4.0 License (CC BY-NC-ND, http://creativecommons.org/licenses/by-nc-nd/4.0/), which permits non-commercial reuse, distribution, and reproduction in any medium, provided the original work is not changed in any way and is properly cited. For permission for commercial reuse, please email: [email protected]. All rights reserved.