CoOx/ZrO2 samples, prepared by adsorption from cobalt solutions or by impregnation, were characterised by means of DRS, XPS, FTIR and volumetric CO adsorption. In samples prepared by adsorption the maximum Co-uptake was 2.2 atoms nm(-2). XPS evidenced cobalt dispersion up to about 2 atoms nm(-2). DRS evidenced Co3O4 above 2 atoms nm(-2). Volumetric CO adsorption, combined with FTIR, showed that cobalt was highly dispersed on the ZrO2 surface in samples containing 0.4 and 0.9 atoms nm(-2). The selective catalytic reduction (SCR) of NO with C3H6 in the presence of excess O-2 was studies on samples containing up to 4.8 Co atoms nm(-2) with a reactant mixture containing NO=4000 ppm, C3H6=2000 ppm, O-2=2%. Isolated cobalt in CoOx/ZrO2 containing up to about 2 atoms nm(-2) is active and selective for NO reduction in the presence of excess O-2. Aggregated cobalt present as Co3O4 in more concentrated samples is active for C3H6 combustion, thus rendering the relevant CoOx/ZrO2 samples non-selective.