The article investigates the determinants of the competitiveness of the banking sector of the national economy on the basis of a comparative analysis of the functioning of the banking systems of Ukraine and Poland.The authors conducted research using the following methoddology: comparative analysis of the institutional efficiency of the banking sectors of Ukraine and Poland; comparative analysis of the level of concentration of the banking sector of Ukraine and Poland; comparative analysis of the microeconomic and macroeconomic efficiency of the banking sectors of Ukraine and Poland; comparative analysis of the social efficiency of the banking sectors of both countries in terms of their financial inclusiveness. The results of the research showed the higher level of competitiveness of the Polish banking system, which is reflected in its stable operation over a long period of time, resilience to crises and excessive risks, effective prudential supervision system, developed institutional structure, close to market and consumer banking needs, and thus dynamic growth of banking financing of national economy and the availability of banking products for businesses and households. In contrast to Polish banking system, Ukrainian banking system in recent years has experienced a deep crisis and a significant number of bank failures, significant amounts of non-performing assets, liquidity problems, etc. and thus in order to save systemically important banks a significant concentration of state capital, extremely high interest rates and as result significant reduction of the share of bank financing of the national economy and the presence of significant barriers to the availability of banking products for consumers. The authors summarized, that the key determinantsof the competitiveness of the national banking sector are the following: the presence of a developed institutional structure of the banking system; prevention of monopolization and excessive concentration of the banking sector; effectively operated national system of banking supervision and regulation; the development of the banking sector as a key player in the national financial ecosystem and fulfillment by the banking system its main functions in the economy and society.