The effect of NO and H2O on the activity of a Cu/V/K/Cl/Ti based catalytic filter in the combustion of soot generated in the flame of a gas-oil burner has been investigated. Temperature programmed oxidation (TPO) of soot collected on a ceramic filter supporting the Cu/V/K/Cl/Ti catalyst was performed with a flow micro-reactor in the absence and in the presence of NO and H2O in the reactant gas. The presence of NO and H2O resulted in a substantial increase of the rate of carbon combustion, and also affected the selectivity (CO2/CO ratio). The enhanced activity is mainly due to carbon oxidation by NO formed by NO oxidation on the same catalyst. TPO test performed after sulphation of the catalytic filter evidenced a marked loss of activity. However, in the presence of NO and H2O the activity of soot oxidation was mostly preserved.