International Science Community Association Research Journal of Recent Sciences 2277 - 2502 3 1 2014 January 2 The Study of the Relationship between Product Market Competition and Capital Structure of Companies Which is accepted in Tehran Stock Exchange 33 37 EN Mohammad Aghaei 1 Department of Business Management, Branch, Shahid Beheshti University (SBU), Tehran, IRAN Amin Asadollahi 2 Department of Business Management, Science and Research Branch, Islamic Azad University, Tehran, IRAN RezaSalehi Nejad 3 Master of Executive Management Business Administration, Science and research Ayatollah Amoli Branch, Amol, Mazandaran, IRAN MahdiAzar Keyvan 4 MohammadiAlamoti Mostafa 5 Mohammadreza Zare 6 Khan Hamna 1 Jinnah University for Women, 5-C, Nazimabad, PAKISTAN Iqbal Munira 2 NarmeenShawoo Bawany 3 FaisalNadeem Saher 1 Civil Engineering and Earth Resources, University Malaysia Pahang, MALAYSIA, Nasly M.A. 2 Computer System and Software Engineering, University Malaysia Pahang, MALAYSIA TutyAsmawatyBintiAbdul Kadir 3 Department of Irrigation and Drainage Malaysia, Kuala Lumpur, MALAYSIA NasehirKhanE.M. Yahaya 4 Centre for Earth Resources Research and Management, University Malaysia Pahang, MALAYSIA WanMohdFaizalWan Ishak 5 MoradyGohareh Mehdy 1 Department of Industrial Engineering, Amirkabir University of Technology,424 Hafez Avenue, 1591634311, Tehran, IRAN Shams GharnehNaser 2 Aminnayeri Majid 3 Javad Heydarzadeh 1 Department of Accounting and Management, Kashan Branch, Islamic Azad University, Kashan, IRAN Hoseyn Jabbari 2 Hasan Ghodrati 3 > Research Paper 2013 5 26 2014 January 2 The aim of this study is to investigate the relationship between product market competition and capital structure of companies which is accepted in Tehran Stock Exchange. The population of study is selected companies listed in Tehran Stock Exchange during the 9-year period from1382 to 1390. Through the populations considered in the Tehran Stock Exchange, a total of 150 companies were selected by simple random sampling method as sample in this study. Capital structure is the independent variable in this study, which it's reagent index according to theoretical considered in this study is intended to debt ratio. The dependent variable in this study is the product market competition which it's index is considered Q2bin, HHI. Also the control variables affecting this study were selected Company size, dividends, interest risk, profitability and non-debt tax savings. The scope of this study includes: a 9-year period from 1382 until the end of 1390 and statistics on these variables are an annual gathering. The results showed that at the corporate level and between the industries, there was no significant correlation between the debt ratio and the earnings volatility (risk-benefit), but four other control variables have a significant relationship with debt ratio. Copyright@ International Science Community Association