A mathematical model was developed for the isothermal absorption of nitrogen oxides into nitric acid solutions containing hydrogen peroxide. This model, based on the two-film theory of absorption with chemical reactions, includes diffusive transport and equilibrium between species in the gas phase and simultaneous absorption of the NOx components with fast irreversible reactions in the liquid phase. Kinetic parameters relative to the absorption of the different NOx species were determined at increasing acidities and for a low concentration of H2O2 from test runs performed in a small packed column at 20 degrees C and atmospheric pressure for various NOx partial pressures up to 500 Pa and the whole range of NOx oxidation ratios. Only the parameter relative to trivalent NOx was found to increase with the HNO3 molarity, the other ones remaining constant. Interpretation of the experimental results according to the model showed that the hydrolysis is the main controlling step for tetravalent nitrogen oxides and that among the trivalent components nitrous acid is likely to be a major transporting species.