Antidecubitus cushion made of slow memory polyurethane foam and a layer of a self-shaping polyurethane gel pad located on top of cushion. The anatomical pre-formed base allows supporting the weight of the patient, adapting to the bone morphology and ensuring the optimal discharge of contact pressure. Moreover the gel layer dampens the pressure on the ischial area. The cover is removable and has antibacterial, waterproof, breathable and bielastic properties. The bielastic characteristic allows a considerable reduction of the friction between the skin and the cushion.The cover is equipped with an anti-slip bottom to assure a safe and stable anchorage to the chair.