Mediastinal paracardiac tumors may cause both cardiovascular complications and problems in differential diagnosis of cardiac diseases. Transesophageal echocardiography (TEE) may give an additional new window to mediastinal neoplasms, but only a few studies have been reported. TEE was performed in 70 patients with paracardiac neoplastic masses. The procedure was indicated to solve particular clinical problems in 20 patients, and as a prospective study on 50 unselected patients with mediastinal neoplasms. Twenty-three patients underwent follow-up studies; a total of 101 echocardiograms were recorded. The procedure was tolerated well or very well by most patients, and provided additional anatomic or hemodynamic data in every patient in group a and in 45 of 50 in group b. The additional data were relevant for clinical management in 14 of 20 patients in group a, and in 3 of 45 in group b. Based on the results of this study, TEE is useful in association with other radiologic techniques in patients with paracardiac neoplasms. As an imaging technique, it may represent a reliable alternative to computed tomography whenever the latter is not feasible.