Introduction: Respiratory diseases are the commonest cause of death in children under 5 year. Pneumonia is the leading killer of children worldwide. In developing countries childhood pneumonias are diagnosed using clinical parameters, usually based on presence of cough and increased respiratory rate. Although this is cheap, sensitive and maximizes the number of children identified and treated empirically, it is also nonspecific and highly dependent on the context in which it is being applied. So the simple chest radiograph has been an important investigative tool in the diagnoses of diseases, since the discovery of X-rays in late nineteenth century. Chest radiograph is frequently used in the management of acute lower respiratory infection in children and still considered to be the gold standard for diagnosing respiratory infection and pneumonia. Objectives: To study the role of chest radiographs in diagnosing the etiology of tachypnea in children less than five years of age and to correlate findings of chest radiographs with etiology of tachypnea. Materials and Methods: A case control study was conducted in the Department of Pediatric Medicine, CNMC, Kolkata on tachypneic children aged between 2 months to 59 months during October 2017 to September 2018, presenting to Pediatric OPD, CNMC (Calcutta National Medical College) with clinical features of tachypnea.