Mediastinal tumors are leading tumors in pediatric chest oncology. Teratogenic mediastinal tumors are characteristic of early childhood. For a period of 7 years 4 children with teratogenic tumors of the mediastinum--7.8 per cent of all mediastinal tumors--have been diagnosed at the Department of Pediatric Surgery, thoracic unit. The authors analyse the clinical symptoms, the tools of diagnosis, emphasizing the diagnostic importance of computer tomography, echography and angiocardiography. All children were operated (total extirpation of the tumor). Three children had benign teratoma, 1 mature teratoma including malignant elements (ECT)). All children were in good state of well-being; in one of them chemo- and radiotherapy is still in progress.