Stoma-leakage collecting device (2), attachment plate (32) and assembly (58) thereof, wherein the collecting device (2) is structured for use together with an ordinary attachment plate (32') for a stoma waste pouch (34). The collecting device (2) is comprised of a plate-shaped body having a surface which is larger than the surface of the attachment plate (32'). The collecting device (2) comprises an inner, liquid-absorbent material (4)； an outer, liquid-tight material (6)； and an opening (8, 10) through the outer and inner material (6, 4), respectively. At least the opening (8) in the outer material (6) is structured for placement around a stoma communication opening (48, 48') in the attachment plate (32'), wherein at least the opening (8) in the outer material (6) is smaller than the smallest transverse dimension of the attachment plate (32'). The distinctive characteristic is that at least a radially inner rim area (12) located around the opening (8) in the outer material (6), is structured in a manner allowing it to be attached in a liquid-tight manner to a rim area (50) of the attachment plate (32').
