The present invention provides a wall for a package, which wall comprises, or includes a layer comprising, a composition comprising a polymer and capable of scavenging oxygen through the metal-catalysed oxidation of an oxidizable organic component thereof. The oxidizable organic component is preferably itself a polymer, and may be the only polymer in the composition. Preferred compositions include a blend of 96% polyethylene terephthalate and 4% poly (m-xylyleneadipamide) containing 200 ppm cobalt as catalyst, with good permeance-versus-time performance (3) when formed into a bottle.