Methanation of CO under unsteady-state operation conditions was studied systematically based on a simplified mathematical model for an integral reactor using steady-state kinetics available in the literature. The inlet composition of CO and H-2 was changed stepwise and the step response of the system was monitored in order to study the dynamic behavior of the reactor. Furthermore, periodic changes were applied with different cycling times. It was observed that the time average reaction rate could not be improved by cycling the feed composition. Moreover, the reactor appears to be self-stabilizing, since the amplitude at the outlet is reduced, leading to a steady state for high cycling frequencies. The results allow conclusions on principles to design a methanation reactor for unsteady-state operation. However, it also becomes obvious that unsteady-state kinetics is mandatory in order to describe the experimental results obtained under dynamic conditions.