A series of 7-week sampling campaigns were conducted in urban background sites of six European cities as follows: Duisburg (autumn), Prague (winter), Amsterdam (winter), Helsinki (spring), Barcelona (spring) and Athens (summer). The campaigns were scheduled to include seasons of local public health concern due to high particulate concentrations or findings in previously conducted epidemiological studies. Aerosol samples were collected in parallel with two identical virtual impactors that divide air particles into fine (PM_2.5) and coarse (PM_2.5-10) size ranges. From the collected filter samples, elemental (EC) and organic (OC) carbon contents were analysed with a thermal-optical carbon analyser (TOA); total Ca, Ti, Fe, Si, Al and K by energy dispersive X-ray fluorescence (ED-XRF); As, Cu, Ni, V, and Zn by inductively coupled plasma mass spectrometry (ICP/MS); Ca²⁺, succinate, malonate and oxalate by ion chromatography (IC); and the sum of levoglucosan+galactosan+mannosan (∑MA) by liquid chromatography mass spectrometry (LC/MS). The campaign means of PM_2.5 and PM_2.5-10 were 8.3-29.6 µg m^-3 and 5.4-28.7 µg m^-3, respectively. The contribution of particulate organic matter (POM) to PM_2.5 ranged from 21% in Barcelona to 54% in Prague, while that to PM_2.5-10 ranged from 10% in Barcelona to 27% in Prague. The contribution of EC was higher to PM_2.5 (5-9%) than to PM_2.5-10 (1-6%) in all the six campaigns. Carbonate (C(CO₃), that interferes with the TOA analysis, was detected in PM_2.5-10 of Athens and Barcelona but not elsewhere. It was subtracted from the OC by a simple integration method that was validated. The CaCO₃ accounted for 55% and 11% of PM_2.5-10 in Athens and Barcelona, respectively. It was anticipated that combustion emissions from vehicle engines affected the POM content in PM_2.5 of all the six sampling campaigns, but a comparison of mass concentration ratios of the selected inorganic and organic tracers of common sources of organic material to POM suggested also interesting differences in source dominance during the campaign periods: Prague (biomass and coal combustion), Barcelona (fuel oil combustion, secondary photochemical organics) and Athens (secondary photochemical organics). The on-going toxicological studies will clarify the health significance of these findings.