A system for treating an aneurysm includes a first double-walled filling structure having an outer wall and an inner wall. The filling structure is adapted to be filled with a hardenable fluid filling medium so that the outer wall conforms to an inside surface of the aneurysm and the inner wall forms a generally tubular lumen to permit blood flow therethrough. The inner wall comprises a blood contacting layer and a reinforcing layer. The reinforcing layer prevents circumferential creep or elastic expansion of the lumen.