Banking sector has been one of the fastest growing sectors in Iran due to changes in regulations in private banks. In this paper, we perform a survey on the effect of structure of financing on banking performance. The main question of this survey is whether there is any relationship between different methods of financing private banks in terms of their performances. The survey investigates relationship between changes in debt ratio with return of assets, between changes in time dependent investments and return of assets, between changes in long-term investments and return of assets. Finally, we study whether there is a relationship between changes in ratio of total equities to total assets on return of assets. The proposed study of this paper considers three private banks whose shares have been traded on Tehran Stock Exchange namely Eghtesad Novin, Parsian and Saman. The information has been collected over the period 2006-2010. The results of this study indicates that there are some positive and meaningful relationships between changes in time dependent investments, changes in long-term investments ratio of total equities to total assets with return of assets. However, the study did not find any meaningful relationship between changes in total equities to total assets and return of assets.

One of the most important issues in financing corporate is to find appropriate method to make a wise selection between getting loans and increasing the number of shares. There are different theories for making appropriate financing methods. The primary purpose of this paper is to investigate this issue based on market timing theory. The proposed model of this paper chooses selective companies from Tehran Stock Exchange. The proposed model of this paper uses regression analysis on two different models. The primary purpose of the first model given in this paper is to study the effect of market timing theory. In this part of survey, we measure the effect of the ratio of market value to book value on the sources of financing firms though increase in equities. Based on the results, we can conclude that as the ratio of market value to book value increases, firms tend to increase their equity though an increase to the number of shares. The first hypothesis of this paper is confirmed. The second model is associated with the relationship with mean ratio of market value on weighted book value and Leverage and the results of this paper do not confirm such relationship.