Support device for persons, such as a bed, treatment or operating table, chair, comprising: - a first and a second movable member (8, 16, 18), 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 (24, 26, 28) associated with the first and second movable member (8, 16, 18), respectively, which hydraulic actuators can each be moved in two directions; - a pump; - a valve assembly which is arranged in the hydraulic circuit between the pump and the respective actuators; the device furthermore being provided with: - a pump activating member which is operatively connected to the pump in order for an operator to activate the pump; - a relief-activating member which is operatively connected to a relief element for removing hydraulic liquid from a selected actuator; - a valve assembly operating member which can be mechanically operated by an operator and is mechanically connected to the valve assembly for providing a connection between a selected actuator and the pump and the relief element, in order to be able to selectively move a movable member by supplying pressurized hydraulic liquid to the selected actuator upon operation of the pump activating member or by removing hydraulic liquid from the selected actuator upon operation of the relief element, respectively, characterized, in that the respective valve assembly is also designed to provide a connection between a selected actuator (24, 26, 28) and the reservoir, the valve assembly operating member being designed such that the selection of an actuator requires a substantially horizontal displacement of the valve assembly operating member into various positions, so that the operator selects the movable member to be moved by operating the valve assembly operating member and produces the movement by activating the pump activating member and the relief activating member, respectively, and the pump activating member, the relief activating member and the valve assembly operating member being designed and arranged as members which can be operated by the operator with his foot and are substantially arranged in a horizontal plane on a longitudinal side of the support device for persons, the valve assembly operating member being situated between the pump activating member and the relief activating member - a first and a second movable member (8, 16, 18), 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 (24, 26, 28) associated with the first and second movable member (8, 16, 18), respectively, which hydraulic actuators can each be moved in two directions; - a pump; - a valve assembly which is arranged in the hydraulic circuit between the pump and the respective actuators; - a reservoir for hydraulic liquid; - a first and a second hydraulic actuator (24, 26, 28) associated with the first and second movable member (8, 16, 18), respectively, which hydraulic actuators can each be moved in two directions; - a pump; - a valve assembly which is arranged in the hydraulic circuit between the pump and the respective actuators; - a pump activating member which is operatively connected to the pump in order for an operator to activate the pump; - a relief-activating member which is operatively connected to a relief element for removing hydraulic liquid from a selected actuator; - a valve assembly operating member which can be mechanically operated by an operator and is mechanically connected to the valve assembly for providing a connection between a selected actuator and the pump and the relief element, in order to be able to selectively move a movable member by supplying pressurized hydraulic liquid to the selected actuator upon operation of the pump activating member or by removing hydraulic liquid from the selected actuator upon operation of the relief element, respectively,