A check valve or non-return valve has a valve body (9) which is connected with a piston (15) by a rod (14). The piston is guided by a sleeve (17) mounted inside an inner housing of the valve. The sleeve is provided with two radially extending openings (21, 22) which are axially spaced from each other. These openings provide communication between the inner space in the sleeve and the inner space in the inner housing (1) depending on the position of the piston (15). This structure permits a rapid closing of the valve, whereby nevertheless, the pressure shock caused by the rapid movement of the valve body is substantially reduced by these openings causing a pressure build-up inside the sleeve with a respective damping action on the valve body.