Particulate matter (PM) and its fraction PM10, belong to the major air pollutants in urban environment, because of their effects on air quality and human health. It is important to study in greater details the impact of different PM10 sources on the mass concentration when exceeding the air quality limit and its target values, observed in Sofia. In order to investigate the PM10 variations in connection with the elemental composition and the influence of the meteorological conditions, winter and summer campaigns with standardized low-volume PM10 sampler were organized at National Institute of Meteorology and Hydrology (NIMH) Sofia, in 2012 In the present paper the results for PM 10 mass concentration and its elemental composition are compared and discussed. In general PM10 concentrations are higher in February (17.7-160.1 μg.m-3) than those measured in July (15.5-42.7μg.m-3), because of the different meteorological conditions. The ED-XRF technique is applied to determine more than 20 elements (P, S, CI, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn Br, Rb, Sr, Y, Zr, Cd, Sn, Sb, I, Ba, Pb) in the filter samples. The concentrations of some of the elements are under the detection limits of EDXDR, in particular for the PM10 summer filter samples. The elemental concentrations are lower in July than in February with an exception for the crustal elements Ca and Fe.