In order to mitigate or completely eliminate the effect of market imperfections such as risk, discomfort, uncertainty, excessive transfer prices, illiquidity, which hamper the direct transfer of funds from the surplus to the deprived business entities, there is a need for financial intermediaries. The most well-known financial intermediary is the bank, along with significant savings deposit institutions, insurance companies, pension funds, money market funds, mutual fund investment funds. The use of external market relationships in the internal business of the bank is called an internal economy in whose center other than interest rates is the evaluation of the efficiency of each organizational part in terms of collecting credit potential and its direction towards those financial entities that need to take into account the market risk and regulatory costs of the bank. Segmentation of individual internal organizational parts of the bank generates profit centers whose existence in most cases is linked to the exploitation of the internal economy. Their basic task is to manage the structural risks that are not subordinated to the accounting recalculation of the profit calculation and possible potential losses. Absolute size is the first aspect of measuring the size of a bank. It is measured by the total value of its entire property that is expressed in hundreds of thousands of dollars, sometimes thousands of US dollars, at the largest contemporary banks. Absolute size is especially important to shareholders and creditors of the bank due to technological and managerial economies and discsonomy of volume, but also because of the "overspending"effect. Expectations of banks to be rescued in case of business problems create a moral hazard that is particularly present in large banks because of the greater likelihood that the state will indeed be saved due to the fear of overcoming the crisis and the negative consequences for the overall financial and economic system. By empirical research we found that the size of the bank is directly related to the financing costs. The cost of financing (interest expense) has a direct impact on the risk structure of the bank's assets, ie the bank is impossible to isolate from the influence of interest rate changes.