In order to elucidate the effect of support in the catalytic performance, two selected potassium-promoted catalysts (K1Cu/beta and KCu2/Al 2 O 3 ) were tested for the simultaneous NO x /soot removal from a simulated diesel exhaust. For comparative purpose, the behaviour of a platinum catalyst (Pt/beta) was also studied. Isothermal experiments revealed that the potassium-promoted catalysts show a high activity for NO x /soot removal in the 350-450°C temperature range. In addition, the catalysts present the advantage that the main reaction products are N 2 and CO 2 . Among the catalysts tested, KCu2/Al 2 O 3 presents the best global performance at 450°C: the highest soot consumption rate, even higher than the platinum catalysts, and a high NO x reduction.