The role of the vitamin D in calcium homeostasis and bone metabolism is well known. In recent years it has been recognized that in addition to the traditional functions, vitamin D modulates a variety of processes such as host defense, inflammation and immunity. Epidemiological data indicate that low levels of vitamin D in serum are associated with impaired lung function and increased incidence of inflammatory diseases, infectious diseases and cancer. The authors studied the correlation among vitamin D levels, allergic inflammation, lung function and control of asthma and found a significant decrease of FeNO values (p= 0.0018) in children with vitamin D levels>30 ng/ml. These findings confirm that vitamin D plays a major role in bronchial inflammation.