Background & objectives: Problems associated with dusts, especially those of smaller than 10 microns, are one of the most important problems related to air pollution. Dusts entering to the atmosphere are driven from arid and semiarid regions. The aim of this study is determination of seasonal air quality variations in terms of PM10 concentration for Kermanshah city over a four-year period (2008-2011). Methods: For this descriptive –analytical study a total number of 1334 samples were collected in different seasons from air pollution measurement stations of Kermanshah Environmental Protection Organization during four years of study. The Data were analyzed by SPSS. Results: Results showed that over the period of 4 years, the total frequency percent of PM10 with good, healthy, unhealthy, very unhealthy, and dangerous criteria were 10.4, 59.2, 26.4, 0.7, and 3.3%, respectively. The respective highest and lowest frequencies of PM10 emissions with good criteria (0-50) occurred in February (37.7%) and June and July (0 %) in winter (21.96%) and summer (4.81%). Conclusion: The results showed that July and summer had the worst air quality in terms of PM10 concentration, which was mainly due to the frequency and intensity of dust entrance in mentioned period of time. Hence, it is necessary to reduce emission of such pollutant sat national management level with cooperation of neighboring country.