A control valve (18) for a device (1) to modify the timing of an internal combustion engine is provided. Here, a controlled rotation of the camshaft in reference to the crankshaft can be achieved via a hydraulic adjustment drive. A control valve (18) with operative connectors (A, B), a hydraulic connector (P), and at least one reservoir connector (T, T.sub.1, T.sub.2) controls the inflow of hydraulic fluid into and/or the outflow of hydraulic fluid out of the hydraulic adjustment drive. A filter (46) is arranged between the hydraulic connector (P) and the operative connectors (A, B).