Modeling is used to study the parametric sensitivity of a heat-integrated methane steam reformer/combustor for hydrogen production. The simulated reformer design is based on structured metal-porous catalysts and the co-current flow mode operation. The modeling results indicate that the reformer has high intrinsic sensitivity to the kinetic activity of reforming and combustion catalysts and to the axial or transversal coefficients of heat conductivity. Moreover, a hysteresis effect with critical points of ignition and extinction was found under synchronous load variation in the reforming and combustion units. These results show that fine tuning of the main design parameters is necessary to avoid both hot spot formation and extinction.