Abstract: An exhaust gas treatment assembly for an exhaust system of an internal combustion engine includes a housing having a circumferential wall and at least one base wall which in an external circumferential region is connected to the circumferential wall. In a housing interior space, which is defined by the circumferential wall and the base wall, at least one exhaust gas treatment unit is positioned so as to be removable from the housing. At least one base wall is an interchangeable base wall which is releasably connected to the circumferential wall via a connection assembly. The connection assembly includes a first connection portion, a first axial support portion, and on the base wall includes a second connection portion which via at least one connection member is releasably connected to the first connection portion and a second axial support portion is supported on the first axial support portion.