The activity and stability of potassium-copper perovskite catalysts for soot combustion were analysed at 450 degrees C in a NOx/O-2 gas mixture. Both impregnated (K-Cu/SrTiO3) and substituted (SrKTiCuO3) copper-potassium catalysts were prepared. For comparative purpose, also a potassium substituted catalyst (SrKTiO3) was studied. The high activity of the fresh potassium catalyst (SrKTiO3) is based on the volatile potassium species reaching the surface of soot. However, this catalyst is not useful because potassium is progressively lost during the reaction. Potassium was stabilized by copper and, as a consequence, the two potassium-copper perovskite catalysts present a constant activity for the soot combustion. The activity of the potassium-copper perovskite catalysts, which is maintained during consecutive reactions, is related to their NO2 production capacity. The metal addition method seems to influence the catalysts performance, the substituted catalyst (SrKTiCuO3) being the most active and stable. (C) 2014 Elsevier B.V. All rights reserved.