Device for preventing decubitus, consisting of a number of adjacent members (1) which are attached to a base and which members (1) are covered with a layer (2) of elastic material which defines a reclining surface for a patient. Each member comprises at least one elastic panel whose two opposite ends are connected to one another via a pulling element (6, 13) in order to pull the two ends towards one another, while bending the said panel, so that the vertical height of the member increases. The device also comprises a control device (3) for activating the pulling element for one or more of the said members as desired. The pulling element preferably consists of a wire, rod or strip of memory metal, which can assume its original contracted position by means of heating.