Pleuropulmonary blastoma is a rare childhood intrathoracic neoplasm, associated with a poor outcome. We report the case of a 7 week-old boy with a pleuropulmonary blastoma classified as type I. Disease was discovered at a chest X-ray performed as a work-up for a benign acute viral bronchiolitis. The final diagnosis was brought by pathology: a bronchopulmonary malformation had not been ruled out by clinical, radiological and macroscopic findings. Pleuropulmonary blastoma is a rare childhood intrathoracic neoplasm, for which the poor outcome and tough diagnosis justify a surgical attitude when an intrathoracic bullous lesion is found in an infant.