The simultaneous reduction of NO + N2O was studied with carbon supported K/Pt catalysts. High conversion levels of both gases were achieved at relatively low temperatures (350 degrees C) and the catalyst stability was confirmed in long duration experiments. A synergistic effect between the two metals was observed under different reaction conditions, and for different metal load combinations, similarly to the effect previously reported for Ni and K. This synergy was analysed and explained in terms of different properties of the system, as well as by the simultaneous participation of K and Pt in the reaction mechanism. (c) 2005 Elsevier B.V. All rights reserved.