Abstract: A device for removing harmful constituents from exhaust gases of internal combustion engines comprises a first housing for conducting exhaust gases, the first housing containing a front, middle, and rear area with at least one intake in the front area and at least one outlet in the rear area. A first structure containing a plurality of contiguous cavities covers the cross-section of the first housing at least partially. The following are disposed in the housing in any sequence: a second structure which contains and/or is coated with a first metal oxide; a third structure which contains and/or is coated with a catalyst for converting or degrading contaminants; and a fourth structure which contains and/or is coated with a second metal oxide. The first housing contains or is at least partially made of or coated with porous aluminum oxide, mullite, cordierite, silicon nitride, tialite, steatite, zircon, zircon dioxide and/or silicon carbide.