The reduction of N2O to N-2 was carried out by temperature programmed surface reaction (TPSR) from 473 to 873 K in He, He + 3% O-2, He + 0.02% NH3 and He + 3% O-2 + 0.02% NH3 on H-FAU supported transition metal catalysts. In the absence of oxygen, the addition of NH3 considerably shifts the N2O conversion profile towards lower temperatures. This is particularly true for the Ru- and Rh-FAU which exhibit the onset of N2O conversion around 500 K. The addition of O-2 inhibits this effect for most of the catalysts and NO formation due to NH3 oxidation is observed. However Fe-, Ni- and Co-FAU kept the best catalytic behaviour for N2O reduction to N-2 in the presence of O-2, when NH3 was added to the feed with respect to the decomposition reaction.