We analyzed the concentrations of organic (OC) and elemental (EC) carbon in fine particulate matter at two regional background monitoring stations in Poland, Diabla Góra and Zielonka, during  30-day winter and summer campaigns  (2016 – 2018). PM1 and PM2.5 samples were collected separately on prebaked quartz-fiber filters using dedicated high-volume samplers for 12 h (days and nights). The mean OC concentrations ranged from 2.23 to 5.68 μg m-3 (PM1) and from 2.32 to 6.91 μg m-3 (PM2.5), with the maximal concentrations of 12.98 μg m-3 (PM1) and 16.21 μg m-3 (PM2.5). The mean EC concentrations ranged from 0.13 to 0.71 μg m-3 (PM1) and from 0.15 to 0.85 μg m-3 (PM2.5), with the maximal concentrations of 2.28 μg m-3 (PM1) and 2.83 μg m-3 (PM2.5). 64 – 94 % of OC and 69 – 86 % of EC in PM2.5 belonged to the PM1 subfraction. Winter OC and EC were higher than summer. PMF modeling with three sources of OC and EC – secondary organic aerosol (SOA), biomass burning (BB), and vehicle emissions (veh) – each split into the local and remote components, provided SOA concentrations consistent with conventional estimates based on the OC and EC concentrations. Winter SOA OC and BB EC were higher than summer. Local SOA OC and EC were larger than the remote, local BB OC was smaller, and local BB OC was smaller than the remote. HYSPLIT analysis showed that the air masses were inflowing to the monitoring site relatively evenly from all directions, with mild prevalence of western inflows at Diabla Góra and west- and southward inflows at Zielonka. PM1 OC and EC concentrations measured at Diabla Góra and Zielonka were only slightly higher than those measured at other worldwide locations, while PM2.5 OC and EC concentrations were comparable.