Pericardial cysts are rare mediastinal abnormalities, which are usually congenital but may also be acquired after cardiothoracic surgery. Cysts frequently occur in the right cardiophrenic angle and their diagnosis is usually suspected after an abnormal chest X ray is obtained. The presence of a pericardial cyst in this typical location or, less frequently, in an unusual location, poses a diagnostic challenge in distinguishing it from other intracardiac or mediastinal abnormalities. Two-dimensional echocardiography and transesophageal echocardiography are extremely valuable in diagnosing the presence of a pericardial cyst. Although most pericardial cysts are asymptomatic, patients may present with chest pain and dyspnea. In addition, life-threatening complications such as pericardial tamponade have been reported in association with pericardial cysts. The following cases illustrate the usefulness of two-dimensional echocardiography in making an accurate diagnosis of a pericardial cyst, as well as in follow-up of these patients for the development of possible complications.