The objective of this article is to try to assess the potential impact of the improved internal quality of the bank on the quality perceived by the customers and on the bank's financial results. The proposed method makes it possible to determine which activities and interdependencies should be taken into account when attempting to improve the bank's performance and what degree of improvement in the performance can be expected if each of the proposed tasks is successfully carried out. In their study the authors used six models relating to the interdependencies between the measurements of internal quality of the bank's branches and the financial parameters as well as between quality assessment provided by bank's customers and the profitability indexes. Using the Data Envelopment Analysis (DEA) and the Malmquist indexes calculated for each model, numerous hypotheses concerning the consequences of improved performance for the profitability and the perceived quality level were verified.

It turned out that the quality of the banking services may have a positive impact on financial results. The greatest improvement of the results should be expected when using quality to determine the optimum volume of transactions. It also turned out that changes in performance as concerns internal and external quality are mainly of technological nature. Changes in the financial variables and financial results lead to both technology and performance improvement (i.e. the units as well as the individual branches become more and more effective as regards the ratio of expenditures and effects). It has also been proven that the results of the quality measurement, using the quality of each type of banking operation, correspond with the quality evaluations made on the basis of features of the banking services. This makes it possible to significantly reduce the costs of quality evaluation in the future.