There are a lot of economic efficiency indicators in theory. It is necessary to choosee some of them for concrete purposes. ROA, ROE and C/I play important role due to last experience of polish banks. Cost to Income Ratio plays very important role affecting not only efficiency monitoring process in the banks but also becoming a very important target in strategy or finance plan. There are several methodological approaches to construct this index in detail. Results are differing due to implementing methodology. This article describes trends C/I concerning both polish and foreign banks. It is difficult to compare banks in emerging country and real giants in finance mature economies.