On PA chest radiography, the anterior junction line(AJL) is seen to project from the upper right to the lowerleft of the upper third of the body of the sternum and represents the visceral and parietal pleura of each lungand a small quantity of mediastinal fat. In a patient with volume loss or expansion of a hemithorax, the AJL showsconsiderable shift and on PA chest radiography may mimic pneumothorax or pneumomediastimum. In such cases,widening and hyperlucency of the retrosternal space, seen on lateral view, which represents herniated lung with ashift of AJL, may be helpful for differentiation from pneumothorax or pneumomediastinum.