A hydraulic unit (5) is provided for a cylinder head (2) of an internal combustion engine with a hydraulically variable valve train (1). In the hydraulic unit, a high-pressure chamber (11), a medium-pressure chamber (12), and a low-pressure chamber (16) used as the hydraulic medium reservoir are formed. The low-pressure chamber communicates via a throttle point (17, 17′, 17″, 17′″) with the medium-pressure chamber, and the throttle point is formed by a displaceable valve body (19, 19′, 19″, 19′″) and has through-flow cross sections of different sizes according to a position of the valve body.