One thousand operated mediastinal tumours are analysed. Their characteristic features are discussed and some uncommon manifestations are presented. It is emphasized that in most cases (80-90%) the traditional simple X-ray methods can give a sufficient information for the diagnosis. On the other hand, vascular lesions, cervicomediastinal goiters, dumbbell neurinomas, lymphatic diseases and esophageal lesions should be detected carefully by especial diagnostic methods before surgery because of the different operative tactics and consequences. The diagnosis of the mediastinal neoplasm indicates surgery due to their compressive behaviour.