Three cases of pheochromocytoma in children/adolescents or young adults treated by 131I-MIBG are presented in this study. In one patient 131I-MIBG was administrated after ineffective surgical treatment and chemotherapy of a benign retroperitoneal tumor, whereas in two other patients 131I-MIBG therapy was carried out because of malignant pheochromocytoma dissemination. In a child with retroperitoneal paraganglioma decrease of tumor size and its fibrosis after 131I-MIBG therapy allowed radical surgery and complete recovery. In two other cases partial remission was achieved. All patients showed a good subjective response with improvement of the general condition and better blood pressure control. In two children adverse reactions such as leucopenia, hypothyroidism or hypogonadism were observed. The presented data confirm effectiveness and acceptable tolerance of 131I-MIBG treatment in pheochromocytoma, what is very important in pediatric patients.