An eight-year-old boy presented with a sudden onset of chest pain. He had been diagnosed to have a left spontaneous pneumothorax. Chest radiographs and computed tomography of the chest showed a thin-walled cyst in the left lower lobe. Thoracotomy and a segmentectomy of the apical segment of the lower lobe was performed, confirming the diagnosis of a ruptured bronchogenic cyst. Imaging findings of various pulmonary cystic lesions in children are discussed.