The aim of our study was to investigate whether the changes of the cognitive functions and activities of daily life occur in the early stage of the hepatic form of Wilson's disease. The experimental group consisted of 17 patients with Wilson's disease as demonstrated by mild or slight liver dysfunction and matched group of healthy individuals on the basis of sex, age and education. Both groups performed several neuropsychological tasks such as The Block Design from The Wechsler Adult Intelligence Scale, The Rey Auditory Verbal Learning Test, The Trial Making Test, and specially designed clinical experiments. The patients did not do as well as the control group in accomplishing most of the neuropsychological tasks. Near statistical significance level was reached when the decline, in patient group, in accomplishing task involving arithmetical and visual-spatial functions. There was no difference between groups in the subjective assessment of the health-related quality of life. Our study shown that in the early stages of the hepatic form of the Wilson disease the cognitive changes are subtle. However we suggest that arithmetic skills and visual-motor functions maybe the first sign of the progressing Wilson's disease.