The present invention provides a method for producing a filled hollow structure, preferably a cushion for a breathing mask. According to said method, a hollow structure of a first material having a cavity is produced, wherein the hollow structure has an inlet to and an outlet from the cavity. The hollow structure is positioned on a tool for holding the hollow structure. Subsequently a second material is inserted through the inlet into the cavity, while gas present in the cavity can escape through the outlet. Finally, the inlet and/or the outlet is sealed. During the step of inserting the second material through the inlet into the cavity the outlet resists flow of said second material.