Echocardiography has become a valuable diagnostic tool in various clinical conditions. Its use for the detection of extracardiac tumors has seldom been reported. The majority of these descriptions are of single case reports. We have recently encountered three patients (two with lymphomas and one with seminoma) who presented with signs and symptoms suggestive of right ventricular outflow tract obstruction. Two-dimensional echocardiography enabled the prompt diagnosis of extracardiac tumors compressing the heart. Moreover, echocardiography proved to be an excellent noninvasive tool for assessing the success of therapy for mediastinal tumors.