Huntington's disease is a rare, although commonly known neurodegenerative disease, caused by dynamic point mutation within the IT-15; it is inherited autosomally dominantly. IT-15 mutation includes multiple (36-250) repetitions of trinucleotide sequence (CAG) encoding a glutamine at the amino end of Huntington (mHtt). It is one of the nine polyglutamine diseases (PolyQ), characterized by a CAG repeat. The pathophysiology of Huntington's disease is associated with dysfunction and loss of neurons and gliosis within the striatum, particularly around the caudate nucleus and frontal lobes. Huntington's disease is characterised by the triad of symptoms: cognitive, motor and psychopathological disturbances. Approximately 80% of patients with HD show some of the mental disorders. The most common are affective disorders, in 30-40% symptoms of depression are present. Depression often precedes the onset of neurological symptoms.