A case of left pulmonary artery sling and tracheobronchial tree malformation is reported in a 3 month-old infant. Acute respiratory presenting symptoms required mechanical ventilatory support. The malformation was suspected because of ventilatory support difficulties. Barium oesophagogram showed an anterior indentation, fiberoptic bronchoscopy and tracheobronchography showed a severe tracheal stenosis from a right bronchus lobaris superior to the carina. This was worsened by the right side compression of trachea end part, due to the abnormal left pulmonary artery as demonstrated by pulmonary angiography. A surgical left artery transposition relieved lateral compression and allowed weaning of ventilatory support. After a 27 month-follow-up, the girl's respiratory status is satisfactory.