Mergers are an increasing phenomenon mainly due to increasing globalization and market competition. Previous research - reporting a high failure rate among mergers - have concentrated on the factors that cause failure or insure success during integration and post merger phases. The purpose of this thesis is to gain a better understanding of the conditions companies should fulfill in the pre-merger phase with the aim of ensuring merger success. Procedures and criteria, as well as role of organizational culture in partner selection were studied through two case studies dealing with mergers of Cloetta Fazer and CashGuard Group. Findings showed that the companies in their pre-merger phases satisfied the conditions leading to a successful merger, even if their ways to success looked different. Regarding the procedure and criteria for selecting a merger partner, our findings generally supported theory, even though Cloetta Fazer and CashGuard Group operate in different industries. When regard to the role of organizational culture and its impact on the pre-merger phase, we found that Cloetta and Fazer had different organizational cultures, while CashGuard and Security Qube System AB (SQS) did not. However, neither of the two companies did a cultural due diligence, as both Cloetta Fazer and cashGuard Group had production collaboration with their merger partners prior to the actual merger.