The application of photocatalytic concrete containing TiO2 in urban streets is a method to improve the air quality in highly polluted areas. By using this technology it is possible to degrade a wide range of air contaminants, like nitric oxide (NO) and nitrogen dioxide (NO2), mainly emitted by automobiles. In the present paper, the photocatalytic degradation of NO and NO2 is experimentally studied, and the atmospheric reactions involving nitrogen oxides and solar radiation are analyzed as well. In addition, the influence of different system parameters, such as inlet pollutant concentration, relative humidity, and irradiance is investigated in detail. (C) 2010 Elsevier B.V. All rights reserved.