Pleuropulmonary blastoma is an uncommon paediatric neoplasm. Approximately 300 cases have been reported. In seven tumours, extension involved the left heart. Type III occurs typically at ages 3 or 4 years. We report this very unusual case of extensive disease in a 16-month old male patient. Chest computerized tomography revealed a mass extending into the right hemithorax from the posterior mediastinum and propagating inside the left atrium through the right pulmonary veins. Echocardiography showed a huge flexible mass occupying almost all of the left atrium cavity and intermittently prolapsing through the mitral valve. Two preoperative chemotherapy courses of ifosfamide, vincristine, actinomycin D and doxorubicin were administered at 3-week intervals. The patient was placed on cardiopulmonary bypass, cardiac arrest and the left atrium was opened. The tumour and orifice of the inferior right pulmonary vein were resected and the normal free borders reconstructed. A large mass occupying the right pleural space was removed. Seven additional courses of chemotherapy were given. In a 'second-look' surgery 6 months later, through a right thoracotomy, the residual mass at the posterior mediastinum was resected. The child received four additional courses of chemotherapy. After 12 months of the initial resection, there is no evidence of recurrence.