Steam reforming of iso-octane in a monolithic type reactor was simulated by a three-dimensional computational fluid dynamics model. The variations of hydrogen production and reactor temperature along the length of the reactor were calculated at isothermal, adiabatic and constant heat flux conditions. The reaction rate expressions based on steam reforming of methane in the Langmuir-Hinshelwood format were used to model steam reforming of iso-octane. The difference between the simulated results and experimental data on hydrogen produced was less than 18%. The results indicated that a large drop in temperature was in the first one-tenth of the reactor under adiabatic conditions with inlet temperatures of 600-900 degrees C. To achieve the same mole fraction of hydrogen (0.27, dry basis) at the exit of the reactor, the maximum temperature difference across the reactor was much smaller at certain heat flux conditions than that at adiabatic conditions. Further, rate of hydrogen production may be evenly distributed in the reactor under certain conditions of constant heat flux. (C) 2008 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.