AbstractCarbonaceous material is a large fraction of urban aerosol and it is classified into Elemental Carbon (EC) and Organic Carbon (OC). EC particles are emitted from combustion sources. Because most combustion sources are anthropogenic and generally EC does not undergo chemical transformations, EC is a good indicator of primary anthropogenic primary pollution. OC particles species are emitted from primary emission sources either anthropogenic or biogenic sources. In this paper we have measured the ground concentration of Particulate Matter (PM), Total Carbon (TC), EC and OC in two Monitoring Stations in Rome. The first station is situated downtown Rome (near S. M. Maggiore Cathedral) where the traffic emission flux is strong. The second station is located in the inner a green park (Villa Ada Park): this site is not directly influenced by anthropogenic emissions. The results show that in Rome the TC contribution is about 30% of PM and the OC/EC vary between 0.5 and 1.5 according to the site we are considering. About the chemical particle composition the longchain carboxylic have been identified as major constituent of organic aerosol and a range values are reported for two important compound class, the Polyciclic Aromatic Hydrocarbons and the nitroPAHs wich are at very low levels.