The banking industry is one of the most active markets for mergers and acquisitions. Several studies show that mergers and acquisitions based on operating performance approach turn out successfully while some show unsuccessfully by not showing performance gains. There are several reasons and this depends on the choice of accounting method. In this study efforts are made to examine the operating performance of bank’s mergers and acquisitions over the period of 2001 to 2006. Furthermore it focuses on its subsidiaries within CEE respectively Kosovo and Romania over a period 2000-2010 by using the accounting data in order to compare the long term performance of acquisition strategy. Over the past two decades a number of changes occurred in the financial banking system by attempting to improve the efficiency, expanding the service and increasing the output. It finds out that the purchase price of banks in the CEE respectively in these two countries is justified. This work provides the rationale understanding of the M&A concept through the literature review respectively it explains the performance of the Raiffeisen Zentralbank’s M&As.