The aim of the research was to determine the influence of selected determinants on the level of cognitive functions in seniors in long-term care and to verify the difference in the determination of cognitive deficits by MMSE and MoCA methods. Design: The work has the design of a cross-sectional quantitative study conducted on the basis of a questionnaire survey. Methods: The population surveyed consisted of 792 residents of long-term care facilities who were included in the sample on a deliberate basis. Quantitative research was conducted using two psychometric tests of MMSE and MoCA. The influence of selected determinants affecting the level of cognitive functions and the difference in cognitive deficit determination were verified by statistical tests: Pearson's chi-square test, Kruskal-Wallis test, Pearson and Spearman's correlation coefficient. Results: The results showed a statistically significant relationship between age (in men ρ =-0.244; Sig. < 0.01) and length of education (ρ = 0.164) and MMSE test results. In the MMSE test, it was also shown that males have a higher incidence of cognitive impairment than women and that more women than men fall into the normal range. The relationship between the results of the MoCA test and the selected variables was not confirmed. The results clearly demonstrated that there is a difference in determining the cognitive deficit between MMSE and MoCA. Conclusions: The research results point to the need to assess cognitive functions and to diagnose their disorders in seniors living in longterm care facilities, especially with reference to the selection of a suitable psychometric tool.