Samples of carbon fiber were prepared from polyacrylonitrile (PAN)-based precursors, covering a range of electrical resistivity from 0.9 to 1,000 mΩ cm corresponding to a range of carbonization heat treatment temperatures (HTT) estimated to be between 700 and 2600°C. Experimental gas diffusion media (GDM) were made from these fibers using conventional phenolic resin/carbon fiber construction, prepared at two different carbonization temperatures (950 and 2150°C). GDM thermal and electrical properties displayed similar trends with respect to fiber and paper HTT. Unexpectedly, GDM bending and shear moduli increased with fiber resistivity, possibly due to shortening of the lower resistivity fiber types during GDM production. Results showed that high HTT of either the carbon fiber or the paper was sufficient to enable average (“wet” and “dry”) 5-cm2 fuel cell performance comparable to current state-of-the-art GDM. A proprietary GDM wet-laid production model predicts a potential cost reduction of about 2% at 20 million m2 annual production by reducing the paper HTT.