The invention relates to a pressure regulating valve comprising a valve body (6) having one or more inlet openings (11) and one or more outlet openings (12) for a pressurised medium, an internal cavity (15) connecting said inlet and outlet openings (11, 12), and a piston (19) which is in contact with a valve seat (16) between inlet and outlet and is axially slidable in the cavity in the valve body against a spring (22), which biases the piston to a closed position, whereby the valve opens when a predetermined pressure acts on the piston. The valve body (6) is provided with an opening (24) at its outlet side (17), where the cross-section of the opening is smaller that the cross-section of the cavity and which opening (24) is in connection with a volume (25) limited by the piston (19) and the lower section of the internal cavity, whereby the pressure drop across the valve dampens variations in the volume (25).