Two different soot samples were produced by acetylene pyrolysis at 1100 degrees C using 50 000 ppmv (soot A) and 5000 ppmv (soot B) initial acetylene concentrations. Both soot samples exhibited different properties. Soot A presented a lower BET surface area, higher C/H ratio, and larger particles than soot B. At 1100 degrees C, soot-NO reaction was analyzed for both soot samples using a wide range of NO concentrations (300-3000 ppmv). Reaction order with respect to NO was determined, according to the shrinking core model with chemical reaction control, resulting in 0.5 for soot A and 0.7 for soot B. The influence of the oxygen presence on soot A and B reaction with NO was also analyzed. At 1100 degrees C and for a given NO concentration of 2150 ppmv, different oxygen concentrations between 250 and 5000 ppmv were tested. The presence of oxygen resulted in some cases in an increase in NO reduction. The analysis of the carbon consumption rates of the experiments in which oxygen was present revealed a competition between oxygen and NO for soot particles.