A turbulent nonpremixed H-2/air flame is simulated using 2D direct numerical simulations coupled with a complete chemical scheme and a detailed transport model. The influence of differential diffusion is evidenced by comparing these results in terms of scatterplots and local flame structures with similar computations using a Lewis number unity hypothesis. The fast chemistry limit and thus the maximum flame temperatures are calculated using one-point equilibrium calculations. The fact that flame temperatures above the maximum flame temperature calculated with the Lewis number unity assumption can be observed with the detailed transport model is discussed and can be attributed to the fact that the mixture fraction and temperature do not have the same diffusion coefficient. A simplified model is proposed to account for this effect. (C) 2004 The Combustion Institute. Published by Elsevier Inc. All rights reserved.