The determination of PAHs in five granulometric fractions of airborne particulate matter below 10 mm has been performed during field campaigns in Bologna and Milan in selected periods during the years 2000 and 2001. In each of the cities three cascade impactors were located at different sites with diverse urban densities and traffic regimes for seven days periods both during the cold season and the warm one. The granulometric spectra have been calculated depicting the mass distribution and the PAH content. The pulmonary model LUDEP developed for radio-protectionistic applications has been adapted and applied for calculating the PAHs deposition in the respiratory tree. The results show that PAHs concentrate in the particulate fraction smaller than 0.4 micron with percentage ranging from 40 to 90 % of the total PAHs adsorbed on PM9 and representing 30-80% of the total mass deposited in the respiratory tree, according to the sampling site and the season.