Abstract: In the positioning system for an operating cylinder (1), a valve or a set of valves (6; 10, 11) comprises means for allowing a free supply of hydraulic fluid from a pump fluid chamber (8) of a pump cylinder (7) into an operating fluid chamber (2) of the operating cylinder (1), for preventing the backflow of hydraulic fluid from the operating fluid chamber (2) into the pump fluid chamber (8) when the hydraulic fluid pressure on the control side (A) rises above a predetermined pressure limit, and for allowing a free back flow of hydraulic fluid from the operating fluid chamber (2) into the pump fluid chamber (8) when the hydraulic fluid pressure on the control side (A) goes below the predetermined pressure limit. An operating piston rod (3) follows closely the movement of a pump piston rod (9), and the valve or the set of valves (6; 10, 11) prevents pressure fluctuations from transmitting from the operating side (B) to the control side (A).