 Background Chronic inflammation in peripheral airways plays an important role in the pathophysiology of asthma. Extrafine hydrofluoroalkane HFA beclometasone is distinguished from other ICS because of its fine aerosol characteristics. As a result, there is a greater extent of deposition of extrafine HFA-beclometasone in the peripheral airways. Therefore, extrafine HFA-beclometasone may have an extra anti-inflammatory effect in children with asthma. 