The assessment of air quality is necessary in order to control and reduce pollution to levels which minimise harmful effects on human health and the environment. This paper describes a method to design air quality monitoring networks for nitrogen dioxide and ozone and its application in Jaen (southern Spain). A fibreglass filter impregnated with triethanolamine was used in diffusive sampling badges for NO 2 determination. For O 3 analysis, sodium nitrite was selected and nitrate, a product of the reaction of ozone and nitrite, was used to assess the ozone concentrations. Sampling campaigns with passive diffusion samplers at 62 sites were then carried out to obtain information on the pollution emissions in Jaen. The sampling campaigns in 2001-2002 revealed an average concentration of 10.4 μg/m 3 NO 2 with maximum values up to 22.5 μg/m 3 in Jaen City centre. The average ozone concentrations were recorded downwind from the emission source, reaching 96.2 μg/m 3 ; the average ozone value in Jaen was 72.0 μg/m 3 . After spatial interpolation of the obtained values with Geographical Information Systems, a selection of the best locations for the monitoring stations was made, in line with the macro-and microscale siting requirements of the European Directive 2008/50/EC on ambient air quality and cleaner air for Europe. A second sampling campaign with diffusive samplers was carried out in 2005-2006 to control if the locations of the air quality assessment stations were still representative for their zone.