An exhaust gas treatment device, especially for an exhaust system of an internal combustion engine of a vehicle, includes a housing (12) elongated in a direction of a housing longitudinal axis (L). An exhaust gas treatment unit (18) is arranged in the housing (12). At least one first exhaust gas guiding device (24) is in flow connection with an axially open axial end area (16) of the housing (12). The first exhaust gas guiding device (24) provides a first flow path area (38) extending along an outer side (22) of the housing (12) as well as a second flow path area (47) connecting the first flow path area (38) with the axially open axial end area (16) of the housing (12).