The objective of this studies is to measure the competitive structure of the Islamic and conventional banks in the MENA region and its determinants. For this, firstly (1) we will use the measuring of the contestability ratios, then (2), we will estimate the model Panzar & Ross (1987). The results show similar changes in two different measures of competition. The banks category analysis revealed that conventional banks are more efficient than Islamic banks. Despite technological changes experienced by the banking system in the MENA region, the analysis of bank competition shows that the concentration of banks in the MENA region is sensitive to variables such as crisis, deposits, capitalization and including variables related to business lines.