A support device for persons, such as a bed, treatment or operating table, chair, comprises: -a frame； -a first and a second movable member, which movable members can be adjusted independently of one another and which are designed to support the person or one or more parts of the person in various positions, and -a hydraulic system for adjusting the movable members, the hydraulic system comprising: -a reservoir for hydraulic liquid； -a first and a second hydraulic actuator associated with the first and second movable member, respectively, which hydraulic actuators can each be moved in two directions； -a hydraulic pump； -a pump activating member which is operatively connected to the pump in order for an operator to activate the pump； -a valve assembly which is provided in the hydraulic circuit between the pump and the respective actuators, and -a valve assembly operating member which can be mechanically operated by an operator and is mechanically connected to the valve assembly for selecting and providing a connection between one of the actuators and the pump in order to be able to selectively move a movable member by supplying pressurized hydraulic liquid to the associated actuator upon activation of the pump.
