Pulmonary artery sling is a rare condition in which the left pulmonary artery anomalously originates from a normally positioned right pulmonary artery. The left pulmonary artery then progresses posteriorly over the right main bronchus near its origin from the trachea, traverses between the trachea and the esophagus and enters the left hilum. Symptoms include cyanosis, dyspnoea and apnoeic spells. It almost always requires surgical intervention. Rarely it is asymptomatic and is detected incidentally in asymptomatic adults.