Perovskite-type oxides (ABO(3)) catalyzed the simultaneous removal of NOx and diesel soot particulates in the presence of oxygen, and were superior to transition metal simple oxides in the selectivity for NOx reduction. Although the catalytic activity of perovskite-type oxides depended on both A-site and B-site cations, the substitution of potassium at A sites prominently promoted the oxidation of soot and the reduction of NOx.