Bruggeman correlation with exponents of m = n = 1.5 (parameters relevant to tortuosity factor) has been extensively applied in the modeling of PEM fuel cells, however, many studies indicated that the usage of m = n = 1.5 will overestimate the gaseous effective diffusion coefficients in the porous mediums of a fuel cell, it is believed that m and n may fall in between 2.0 and 5.0, but with different values. This paper attempts to investigate the sensitivity of the gaseous diffusion to the various reported values of m and n by a three-dimensional two-phase fuel cell model to answer how much difference they will make in predicting cell performance. The numerical results demonstrate that the cell performance varies considerably with the variation of m and n, and the sensitivity of cell performance to m and n in cathode side and anode side, in GDL and CL can be of great distinction. (C) 2016 Elsevier Ltd. All rights reserved.