A control valve (1) of a camshaft adjuster, which has a housing (2) having three pin openings (5a, 5b, 5c), spaced apart axially from each other, wherein two pin openings (5a, 5b) are each connected to the tank connection (T) in two axial positions of the control piston (4) and the third pin opening (5c) is not connected to the tank connection (T) in a third axial position of the control piston (4) in a fluid-conducting manner.