The storage of NO2 and NO/O-2 in the presence and in the absence Of CO2 was investigated at 350 degrees C on Pt-Ba/Al2O3 LNT catalysts and on the reference Ba/A1203 system, by coupling in situ FVIR spectroscopy and transient response method (TRM). Experiments were performed by admitting NO2/CO2 or NO/O-2/CO2 mixture (CO2/NO, ratios in the range 1-7) or, in alternative, by admitting NO2 or NO/O-2 on catalysts previously saturated by flowing CO2.