The main purpose of this work is to estimate the air pollution effects of 2003 forest fires through the application of two air quality modelling systems (CHIMERE and LOTOS-EUROS) over Portugal and its intercomparison. Forest fire emissions were estimated based on specific southern European emissions factors, on type of vegetation and area burned, and incorporated in the emission input data of both modelling systems. Results showed a significant performance improvement when forest fires are taken into account. PM10 and O3 values can reach differences in the order of 30%, showing the importance and the influence of this type of emissions from local to regional air quality. The different results of the two models may give an indication of the uncertainty associated by using different models to investigate the impact of forest fires. Historical datasets of area burned, number of fires and air quality data were evaluated from 1995 to 2005 aiming to investigate a potential relationship between forest fire activity and air pollutants concentrations. The obtained results point to statistically significant correlations between fire activity in Portugal and PM10 and O3 levels in the atmosphere.