In a pneumatic damper for slowing down movable furniture parts, comprising a cylinder and a piston movably disposed in the cylinder so as to form a displacement chamber at one side and a vacuum chamber at the other side of the piston, the piston includes a seal element which, in one end position thereof, is in close contact with the wall of the cylinder whose cross-section increases toward the opposite end of the cylinder so that the sealing effect collapses when the piston approaches its other end position and the piston includes a piston rod, which has a diameter of less than 35% of the piston diameter and sealingly extends through a cylinder end wall.