Hydroelectrolytic disorders often complicate surgery of intra/parasellar tumors in children and adolescents. Eighteen patients undergoing microneurosurgical procedures for intra-supra-sellar craniopharyngioma (10 patients), hypothalamic germinomas (3 patients), hypothalamic-chiasmatic astrocytomas (3 patients), pituitary adenomas (2 patients) were studied. The hydroelectrolytic balance was assessed from 8 hours before surgery to 1 week after with a specific protocol in which water metabolism alterations were treated with standard procedure. Diabetes insipidus (DI) was observed in 10/18 patients before surgery and in 15/18 patients after surgery; during surgery it was effectively treated with synthetic desmopressin (DDAVP) and hydroelectrolytic solutions. Hyponatremia, isolated or associated (with diuresis contraction or polyuria), seen during surgery and in the following 24 hours, was treated with variation of the infusion rate. We show that close monitoring and treatment of hydroelectrolytic disorders in patients submitted to neurosurgery for intra/ parasellar tumors may significantly reduce their morbidity and mortality rate.