The aim of the article is to analyse operational efficiency of nine commercial banks separated from the National Bank of Poland in 1989. The background of this analysis is a presentation and evaluation of principal institutional and economic factors that do influence the banking sector. The notion of operational efficiency of this sector can be defined as an ability of banks to operate effectively their current activities under market circumstances and competition. Operational efficiency during macro-economic transformation depends heavily on external factors particularly, institutional ones. The impact of these factors stems from the need to implement deep changes in qualitative policy changes in economic structure and in the role o...