Preoperative preparation of the patients with adrenal cortex dysfunction is based on the careful preoperative evaluation of the type and the severity of the disturbance. The dysfunction involving adrenal glands may be: insufficiency (severe, mild, expressed) and hyperfunction (hypercorticism and/or hyperaldosteronism). If we speak about the patients with limited adrenal reserve (Addison's disease, therapeutic glucocorticoid application etc.) they need necessary corticosteroid supplementation, during preoperative preparation, as well as, during complete perioperative period. Doses needed for the substitution are adjusted according to the severity of adrenal insufficiency and according to the extent of the planned surgical procedure. Patients with Cushing's syndrome (or other form of hypercorticism), as well as, patients with Conn's syndrome (or other forms of hyperaldosteronism), do have numerous organ dysfunctions, that are significant in preoperative preparation, anesthesia and for the outcome of the surgical treatment. Common feature for both of the above syndromes is hydroelectrolyte disbalance, with hypokalemia, metabolic alkalosis and hypertension. Disturbances related to the adrenal cortex hyperfunction must be corrected preoperatively, in order to avoid complications. When we speak about hypokalemia it must be promptly corrected even before urgent/vital surgical procedure because it may cause severe intraoperative cardiac arrhythmia.