An 8-year-old girl, without any previous medical history, presented with a first short syncope. Physical examination was unremarkable. Transthoracic echocardiography revealed a thin-walled, echo-free cystic structure adjacent to the posterior wall of the left ventricle, and compressing it moderately. Other echocardiographic findings were normal. Both computed tomography and magnetic resonance imaging suggested a simple pericardial cyst, but during surgery we found an epicardial cyst with partial involvement of the circumflex branch of the left coronary artery. Cardiopulmonary bypass was necessary for successful resection of the cyst, leaving behind only the small area in continuity with the coronary artery.