Cognitive impairment is a common disease. Many studies attempt to explain the mechanisms of these dysfunctions formation, including correlations between cognitive functions and biochemical parameters. Scientists search for substances that would be indicators of cognitive functions and which could be determined in the cerebrospinal fluid or blood of the subjects. To date, they have isolated a few of such substances; however, research on their specificity, validity and the possibility of their use in diagnostics and prognostic assessment is still ongoing. However, there have been only few reports in the literature systematizing the existing knowledge on this subject, and they are mostly related to Alzheimer's disease, not cognition in general, or referring only to a specific group of substances. This article discusses the most important biochemical exponents of cognitive functions.