The paper deals with the relationship of homeostatic and motivational disorders in the postoperative clinical picture in basal-diencephalic tumors. The material included 354 clinical observations of: hypophysial adenoma (n = 135); craniopharyngioma (n = 71); tumors of the third ventricle (n = 88); basal meningiomas (n = 60). A comparative analysis of the findings allowed the authors to support that there are typical variants of changes in the patients' status, which reflect the nature of ion-osmotic disorders. The most significant mental disorders were transient hyperosmolar-hypernatriemic disturbances. The poor predictors were persistent hypernatriemia concurrent with evolving coma, systemic hemodynamic and respiratory disorders. Hyponatriemia is a better predictor of ionosmotic disorders, which requires a careful postoperative monitoring and a comparison of its findings with the specific features of intensive care performed.