In patients with advanced cirrhosis with ascites disorders of water and electrolyte metabolism are often present and they are associated with changes in acid-base balance. These changes can be very complicated, their diagnosis and treatment difficult. Dilutional hyponatremia is the most common disorder. Hyponatremia in these patients is associated with increased morbidity and mortality before and after liver transplantation. Other common disorders include hyperchloremic acidosis, hypokalemia, metabolic alkalosis, lactic acidosis, respiratory alkalosis. If renal impairment occurs (for example hepatorenal syndrome), metabolic acidosis and retention of acid metabolites may develop. The pathogenesis of these conditions applies primarily hemodynamic changes. Activation of renin-angiotensin-aldosterone system and non-osmotic stimulation of antidiuretic hormone trigger serious changes in water and natrium-chloride metabolism. This activation is clinically expressed like oedema, ascites, hydrothorax, low to zero natrium concentration in urine and increased urinary osmolality, which is higher than serum osmolality. In practice, the evaluation can be significantly modified by the ongoing diuretic therapy. Closer monitoring of water and electrolyte metabolism together with acid-base balance in patients with ascitic liver cirrhosis is important, not only in terms of diagnosis but especially in terms of therapy.