A case of 19-year-old male with idiopathic diabetes insipidus diagnosed 9 years ago. 1.5 years from the onset of the disease vision disturbances, neurologic deficiencies and symptoms of hypopituitarism showed up. MRI examination revealed an advanced hypophyseal and pineal gland tumor--germinoma. Total regression was achieved with radio- and chemotherapy. For 7 years from the end of treatment patient has not declared any complains except for vision disturbances and hypopituitarism has been substituted successfully. The case puts on the necessity of a strict endocrinologic and radiologic follow-up in patients with idiopathic diabetes insipidus due to the possibility of existing potentially curable disease ie. intracranial tumor.