Vitamin D deficiency is increasingly being recognized as a prevalent problem in the general population. Patients with chronic lung diseases such as asthma, cystic fibrosis, chronic obstructive lung disease and interstitial pneumonia appear to be at increased risk for vitamin D deficiency for reasons that are not clear.Several studies indicate that vitamin D possesses a range of anti-inflammatory properties and may be involved in processes other than the previously believed functions of calcium and phosphate homeostasis. Various cytokines, cellular elements, oxidative stress and protease/antiprotease levels appear to affect lung fibroproliferation, remodelling and function, which may be influenced by vitamin D levels. Chronic lung diseases such as asthma and chronic obstructive lung disease have also been linked to vitamin D on a genetic basis. This immune and genetic influence of vitamin D may influence the pathogenesis of chronic lung diseases. A recent observational study notes a significant association between vitamin D deficiency and decreased pulmonary function tests in a large ambulatory population.The present review will examine the current literature regarding vitamin D deficiency, its prevalence in patients with chronic lung disease, vitamin D anti-inflammatory properties and the role of vitamin D in pulmonary function.