A lung-volume-reduction device for treating a lung to relieve symptoms of chronic obstructive pulmonary disease and/or emphysema. The device includes a chest-mounted housing and a conduit which projects from the housing through an aperture in the chest of the patient into the lung. The other end of the conduit is connected to flow-control device which may include a valve such as a one-way valve, check valve or pressure-actuated valve. The flow-control device is positioned within the chest-mounted housing. The lung-volume-reduction device permits gasses to pass through the conduit and flow-control device and vent to atmosphere external of the patient.