It is known that hyperuricemia is recognized as an independent cardiovascular risk factor. However, uric acid can also perform useful functions due to its antioxidant properties, which may be especially relevant in the context of neurodegenerative diseases. This review examines the currently available data on the relationship between serum uric acid levels and cognitive functions in the elderly, paying special attention to the etiology of cognitive disorders (Alzheimer’s disease, Parkinson’s dementia and vascular dementia). Despite the high heterogeneity of existing studies due to the different characteristics of the studied populations and methods of assessing cognitive impairment, it was concluded that uric acid can modulate cognitive function in different ways depending on the etiology of dementia. Modern studies demonstrate that uric acid can have a neuroprotective effect in Alzheimer’s disease and Parkinson’s dementia, while hypouricemia is a risk factor for faster disease progression and is a possible marker of malnutrition. Conversely, a high level of uric acid in the blood serum can negatively affect the course of the disease in vascular dementia. Further studies are needed to clarify the physiopathological role of uric acid in various types of dementia and its clinical and prognostic significance.