Banks face various risks in their operations. Inadequate management of such risks leads to the deterioration of bank business performance and, in the worst case, to bank failure. One of the most significant risks banks face is related to liquidity risk. Adequate management of liquidity in banks implies establishing an appropriate relationship between bank assets and liabilities and the possession of appropriate liquidity reserves. This paper researches the relationship and connection between liquid assets and certain bank balance sheet items as internal determinants of liquidity. The goal of the research is to determine the correlation between the liquidity reserves of banks, in this research, the liquid assets of banks, with selected balance positions, namely total deposits, citizen deposits, capital and bank loans, within the banking sectors in Bosnia and Herzegovina, Serbia and Montenegro. Liquid assets are determined as a dependent variable, and the aforementioned banks’ balance sheet positions represent independent variables. The research was conducted for the period from 2000 to 2022 for the banking sectors in the Republic of Srpska and the Federation of Bosnia and Herzegovina, from 2002 to 2021 for the banking sector in Montenegro and from 2003 to 2019 for the banking sector in Serbia. The results of the research showed a correlation between the observed variables, with a difference in the intensity of the correlation and the level of unit changes across the banking sectors. The conducted research also opened up new directions of scientific research regarding the analysis of bank indicators associated with crisis situations common to modern business conditions, as well as macroeconomic factors that can impact bank liquidity, including banking regulation and the financial safety net.