We present a patient of 2.5 years of age with hemophilia A and a pulmonary hydatid cyst. A chest x-ray taken by chance showed a paracardiac opacity resembling an intrapulmonary hematoma which did not reduce in size after infusions of fresh frozen plasma and factor VIII but rather enlarged. Transabdominal ultrasound, colored echocardiography, thoracic computed tomography and magnetic resonance imaging findings were consistent with a cyst that was firmly attached on the border of the right atrium and also indented it; the wall was remarkably thick with no internal echoes. Hydatid cyst was diagnosed after thoracotomy.