The selective catalytic reduction (SCR) of NO by decane under an oxidising atmosphere has been carried out on Cu/ZrO2 and Cu/ZrO2(SO42-). Zirconia-supported Cu catalysts were prepared by ligand exchange with Cu acetylacetonate followed by calcination at 773 K. The solids obtained were characterised by temperature programmed reduction (TPR) by hydrogen and temperature programmed desorption (TPD) of NO. Cu/ZrO2 is active and selective in the reduction of NO by decane at low temperature (< 600 K) but oxidises NO to NO2 between 640 and 770 K. By contrast, whatever the temperature, a total selectivity to nitrogen is obtained with Cu/ZrO2(SO42-). About 40% NO conversion to N-2 is observed with GHSV of 70 000 h(-1). The promoting effect of sulfate is attributed to the large increase of acidity and the strong interaction between copper and sulfur species which is evidenced by TPD of NO and TPR by H-2.