Juvenile laryngotracheal papillomatosis spreads to involve the lungs in less than 1% of cases, and when this occurs, the prognosis is poor. In seven such cases, the lung lesions, which appeared either solid or cystic on radiographs, proved to be benign squamous cell proliferations or papillomas, with central cavities containing debris or air. They seemed to grow centrifugally, using the alveolar walls as scaffolding with central coalescence and lung destruction. Papillomas spread inferiorly from the larynx by direct extension as far as the major bronchi, but rarely beyond. However, the parenchymal lesions were widely scattered, and some were subpleural. This discrepancy suggests that fragments become detached, particularly during endoscopic resection, and are carried down the airways by airflow. Those that lodge proximal to the respiratory bronchioles may be removed by mucociliary action and cough. Those that travel more distally are poorly cleared and may grow. If enough lung parenchyma is destroyed, the patient can develop symptoms of restrictive lung disease in addition to signs of upper airway obstruction.