A wound dressing comprising: an air-impermeable backing sheet having an aperture for attachment of a suction element an air-permeable screen layer on a wound facing side of the backing sheet and a substantially air-impermeable hydrogel layer extending across a wound facing side of said screen layer and joined in substantially airtight fashion to a periphery of said backing sheet around said screen layer. Also provided is a wound treatment system comprising a wound dressing according to the invention and a source of suction in fluid communication with said aperture.