Ambient samples of coarse and fine organic particulate matter collected from two urban sites in the city of Athens over one warm and one cold period have been solvent-extracted and quantitatively characterized by gas chromatography-mass spectrometry for their content of polycyclic aromatic hydrocarbons (PAHs) and oxidized PAHs (oxyPAHs). Variable concentrations were observed for the two distinct monthly periods representing a cold, dry period and a summer period, relating to strong local primary emissions and to lower emissions with more stable meteorological conditions, respectively. Additionally, gaseous concentrations of selected PAHs were calculated, revealing that the relative proportions between gaseous and particle phase of individual compounds may differ significantly between summer and late winter, reflecting changes in PAH emission sources and climate conditions. In fact almost all of Sigma PAHs were attributed to combustion sources (82-92%), while more than half are considered as comprising of probable human carcinogens (47-62%). Traffic was confirmed as the major contributor of PAHs when appropriate diagnostic ratios and traffic marker compounds were used. This approach also led to the estimation of diesel versus petrol contribution to the atmospheric PAH burden, using the methylphenanthrene to phenanthrene ratio. The fourteen oxygenated polycyclic compounds that were quantified had greater concentrations in the colder period. Among these compounds 9,10-phenanthrenequinone, 1-pyrenecarboxaldehyde and 9H-fluoren-9-one had the highest concentrations. (C) 2009 Elsevier B.V. All rights reserved.