A method and a device for monitoring the intake manifold pressure of an internal combustion engine in which a measured signal for the intake manifold pressure is compared with a reference signal for the intake manifold pressure. For a deviation of the measured signal for the intake manifold pressure from the reference signal for the intake manifold pressure, a tolerance range is predefined for error-free operation of the intake and/or exhaust valves of at least one cylinder of the internal combustion engine. A check is made whether the measured signal for the intake manifold pressure deviates from the reference signal for the intake manifold pressure by more than a predefined tolerance range. In this case an erroneous operation of the intake and/or exhaust valves is detected; otherwise an error-free operation of the intake and/or exhaust valves is detected.