We have found that none of the analysed polymorphisms in the genes of renin-angiotensin system, i.e. rs699, rs4762 in AGT, rs5186 in AGTR1, rs5194, rs1403543 in AGTR2 or ACE I/D was associated with MCI or dementia in Parkinson’s disease. The gene discussed is REN; the disease is Parkinson disease.