C-type cubic (Yb1-xTbx)(2)O-3 +/-delta (0 <= x <= 0.62) catalysts were synthesized by coprecipitation. Among the samples prepared, (Yb0.50Tb0.50)(2)O-3 +/-delta showed the highest catalytic activity and high tolerability for O-2 or CO2 coexistence was recognized. In particular, the negative effect of CO2 on the NO decomposition activity is significantly reduced compared to those of conventional catalysts, and N-2 yield as high as 33% was obtained even in the presence of 5 vol % CO2.