Mathematical simulation results are compared for several types of reactors for the conversion of methane to synthesis gas via catalytic partial oxidation of methane coupled with the simultaneous steam reforming. The simulations concerned reactors operating under non-stationary conditions, i.e. at a continuous, forced unsteady state. Both reverse-flow reactors with pelletized and monolith catalyst were simulated, and those with the pelletized catalyst, operating under conditions of feed composition cycling. The simulation results were compared with data for similar reactors operating at steady state. The basic process parameters compared include the conversion of methane and oxygen and the selectivities of the products (CO and H-2). To provide a comprehensive assessment of the simulation results, thermodynamic conditions for the formation of permanent carbon deposits were also analysed.