Abstract: A process for manufacturing a cushion made of polyurethane foam covered with a cover comprises the initial step of placing the cover in a mould having the shape of the cushion to be obtained, the cover having a front face forming the exterior decoration layer which is placed against the inside wall of the mould and a rough back face facing towards the inside of the mould. Then a film of thermoplastic material is placed on the rough back face of the cover, the film containing agents reacting with polyurethane isocyanate, the film being initially permeable to water vapor. Then polyurethane is injected into the mould to form said foam by expanding. The film has a plastification capability under the effect of chemical reactions occurring between the material of the film and the isocyanate contained in the polyurethane.