Subclinical hepatic encephalopathy (SHE) is a serious clinical problem in patiens with liver damage and precise pathophisiological mechanisms resonsible for encephalopathy are not fully understood. Is definied as a spectrum of neuropsychiatric abnormalities in patients with liver dysfunction after exclusion of other known brain disease. Recent date have shown that increased CNS (central nervous system) ammonia concentration and presence of mild diffuse brain oedema plays a key role in the pathogenesis of SHE. Diagnosis of manifest HE (hepatic encephalopathy) is made on the basis of clinical symptoms, whereas psychometric or neurophisiological tests are required for detection of SHE. PET, MRI, H-MRS allow the rapid and noninvasive evaluation of structural, phisiologic and biochemical features of the brain.