This research studies an ultra-thin carbon fiber paper fabrication process for proton exchange membrane fuel cells (PEMFCs). Polyacrylonitrile (PAN) based carbon fibers 6 mm long were dispersed and formed at aerial weights of 15 and 20 g/m(2) using a slurry molding machine. Polyscrylamide (PAM) and polyvinyl alcohol (PVA) dispersal agent solutions for fiber binding were added to evenly distribute the carbon fibers and increase the paper mechanical strength. The carbon fiber papers were dried after resin impregnation using a convective oven at 120 degrees C temperature for 10 min. The hot press machine was heated to 160 degrees C temperature and the workpieces were pressed for 5 min. Graphitization completed the gas diffusion substrate (GDS) process. GDL involves immersing the paper in a 5% polytetrafluoroethylene (PTFE) solution, coating the paper with a micro porous layer (MPL). This study shows the proposed ultra-thin GDL fabrication method is suitable for PEMFC applications and exhibits feasible functionality for fuel cells. Copyright (C) 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.