Resumen
This study investigates the effects of ownership structure on the performance of the listed companies in Borsa Istanbul Stock Exchange 30 Firms (BIST 30). The main hypothesis of our study is that there is a significant relationship between companies' performances and their ownership structures.The statistical population includes 19 non-financial companies in the period of years between 2008 and 2013. The results show that the concentration of the large shares of companies one or a few share holders has a negative effect on related firm?s performance.