Presentation of potentially malignant tumours, highly frequently found in children, developed out of embrionary remnants. Study of clinical observation files, iconography resources, histopathological samples and surgical operation notes, corroborated with patient's reexamination several years later. There are presented nine clinic cases of tumours found in newborn, babies and even in young children, with teratome-like structure, that have malignant potential if excised late. Histopathological laboratory tests of the biotic sample are of paramount importance in establishing the structure of the tumour, its malignization abilities and the therapeutical conduct to be adopted. Other useful investigations: radiographs of the vertebral column, abdominal echographs, computerized tomography. Besides sacrococcygian, large and anesthetic, location in newborn, there are presented cases of intra-abdominal teratomes and one case of ovarian teratome. The study also contains a general opinion upon the patients operated on the reexamined several years later.