Background: Vitamin D has long been known to play a role in the skeletal system and calcium homeostasis; the deficiency of which causes rickets and osteoporosis. There is growing evidence that vitamin D also contributes positively to pulmonary health. Vitamin D deficiency is a common and important nutritional deficiency in children in India. Clinical and subclinical vitamin D deficiency in children has been reported to be a significant risk factor for severe acute respiratory tract infection. The aim of this study to compare the evaluation of the association of acute respiratory tract infections with serum vitamin-D levels in children between 2 months to 5 years of age.