The relationship between capital structure and performance in Gulf Countries Banks, came under the spotlight in a comparative study between Islamic Banks and Conventional Banks. The study was conducted by Associate Professor in Finance and Banking at Kingdom University Dr. Abdelrhman Meero. According to Professor Meero, it is imperative to conduct continuous studies and research in this field, especially as new trends and regulations are periodically introduced by governing authorities in this sector. Results of the study show that there is a similarity of capital structure of Islamic banks and Conventional banks in Gulf Countries. The similarity of capital structure could be the result of the regulation system of the Gulf Countries, which controls the two types of banks by the same capital adequacy regulations.