Adsorption of NO2 and retention of NO (the product of NO2 reduction by carbon) on iron-containing materials prepared from polystyrenesulfonic acid-co-maleic acid iron salt were studied. The surface of the materials was characterized using nitrogen adsorption, XRD, scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray (EDX), and FTIR spectroscopy, and thermogravimetric analysis (TGA). The results showed the positive effects of the pore volume and well-dispersed iron species (Fe2O3, FeSO4, and FeS) on the performance of carbons as NO2 adsorbents at room temperature. The retention of NO2 on the carbon surface takes place either through its reduction to NO by carbon and/or by Fe2O3, FeSO4, and FeS, or through its reaction with Fe2O3 and/or Fe(OH)3, leading to the formation of Fe(NO3)3. The retention of NO is enhanced on carbons containing iron in the form of α-FeOOH, α-Fe2O3, or γ-FeOOH. The best performance was found on the carbon with α-Fe2O3. Dispersion and the particle size of iron compounds on the carbon surface affect both the adsorption/reduction process of NO2 and the retention process of NO.