Pulmonary hamartoma composed of an abnormal mixture of mesenchymal elements is the most common benign neoplasm in the lung. Pulmonary hamartoma larger than 10 cm and the cystic variant are also very rare. We describe an asymptomatic 11-year-old boy with a huge mass in the right hemithorax. Chest computed tomography revealed a heterogeneous mass filling the middle and the lower lobes of the right lung. The patient underwent thoracotomy and resection of the lesion. Gross examination of the surgical specimen showed a well-circumscribed, encapsulated, lobulated, and bluish-white mass, measuring 18 x 16 x 8 cm. Multilocular cystic spaces with intervening lobulated fragments of cartilaginous tissue and adipose tissue were seen. Microscopically, the solid component was composed of cartilage and adipose tissue. Cystic areas and cleft-like spaces were lined by ciliated columnar epithelium. We believe this is the first case of 'giant cystic chondroid hamartoma of the lung' described in childhood. We suggest that giant cystic pulmonary hamartoma should be included in the differential diagnosis of large intrathoracic masses in children. (c) 2008 Elsevier Inc. All rights reserved.