Episodic regional air quality problems maybe occasionally associated with atmospheric blocking phenomena (defined as long-lived and recurrent system which does not progress at all within the latitude belt of baroclinic westerlies). Two episodic cases with severe air quality degradation, smoke in May 2003 and Asian dust in April 2006 were investigated to understand their relationships with atmospheric blocking over East Asia. In order to detect atmospheric blocking over East Asia and its surrounding region, the persistent positive anomaly method for 500 hPa geopotential height field is applied. The result shows the close relationship between the blocking phenomena and long-range transport process of atmospheric aerosols. Persistent positive and negative anomalies of large-scale circulation systems were found by the time-longitude cross section analysis of the geopotential field. The anomalous blockings seem to be linked with high atmospheric loadings of smoke and dust aerosols which are resulted in prolonged air quality problems in Korea and East Asian countries.