The aim of our study was to assess the ability of echocardiography to recognize mediastinal masses. We studied 50 patients: 25 with acute lymphoblastic leukemia, nine with lymphomas, four with pleural effusion and previously known neoplastic diseases, ten with nonlymphomatous mediastinal masses, and two with compression of the superior vena cava. In 33 of 50 patients, computed tomography (CT) showed mediastinal masses, and in one, an aneurysm of the thoracic descending aorta. All patients had previously had chest x-ray and two-dimensional echocardiographic (2-DE) examinations in order to recognize the presence of masses. Two-DE was found to have similar specificity (94.1 percent) but higher sensitivity (90.9 percent vs 60.6 percent) if related to radiographic examination. The positive predictive value was 96.7 vs 95.2 percent and the negative predictive value was 84.2 percent vs 55.1 percent. In particular, 2-DE was more useful than chest x-ray examination when a concomitant pleural or pericardial effusion was present. Moreover, abnormalities of cardiac function due to compression or infiltration and the follow-up of patients were better evaluated.