A respirator with a tidal volume-measuring device (6) between a respiration bag (8) and a patient adapter (2) provides accurate metering of the tidal volume. The device includes a first pressure-measuring device (4) and a breathing gas interruptor (5) in series sequence between the patient adapter (2) and the tidal volume-measuring device (6). A second pressure-measuring device (7) is provided between the tidal volume-measuring device (6) and the respiration bag (8). A control unit (20) is connected with the tidal volume-measuring device (6) and the pressure-measuring devices (4, 7) and sends control signals in such a way that when a predetermined tidal volume is reached, the breathing gas interrupter (5) is switched to the closed position, and that the closed position is eliminated when the pressure p₂ measured with the second pressure-measuring means (7) has dropped below the pressure p₁ determined with the first pressure-measuring means (4).