The present invention is related to a cushion (1) for a respiratory mask, to a method of manufacturing such a cushion (1) as well as to a respiratory mask including a cushion (1) and an apparatus for manufacturing a cushion (1) for a respiratory mask. It is particularly referred to a method of manufacturing a cushion (1) for a respiratory mask, comprising the steps of providing a mold comprising at least two mold halves (11, 13) and at least one core (12) therein, closing the mold, injecting a first material into the mold to form the cushion (1), wherein the core (12) is enclosed by the cushion (1) thereby forming at least one cavity (4), opening the mold, removing the core (12) from the cushion (1) to provide the at least one cavity within the cushion (1), and sealing the cavity (4).