Mergers and acquisitions have different meanings depending on the definition. A merger is the union of one or more companies with another without the transfer of assets, while an acquisition is the creation of an entirely new company consisting of two or more companies that lose their legal personality. The objective of this thesis is to draw a conclusion about the success of mergers and acquisitions through a comparative analysis of the activities of the observed companies. Two research questions are defined: What was the impact of the mergers or acquisitions on the observed companies and In what way did the merger and acquisition activities affect the overall performance of the company? The theoretical part of the paper explains the basic concepts and breaks down in more detail the types of mergers and acquisitions of companies, the stages of the process, and the mergers and acquisitions that have occurred throughout history. The theoretical part also addresses the motives, risks, advantages and disadvantages of corporate mergers and acquisitions, as well as the methods used to measure their success. In the empirical part of the paper, the analysis is carried out using specific examples of retail companies. Secondary data available on the website and on the official website of the analyzed companies were used for the analysis. In particular, the descriptive method, generalization method, financial analysis method, statistical method and inductive method were used in this thesis. The analysis of horizontal integration is performed on the example of the acquisition of Splitska banka d.d. by OTP banka d.d. in the period from 2017 to 2021. After the merger, OTP banka d.d. becomes the fourth largest bank on the Croatian banking market and records positive business performance. The analysis of vertical integration is performed on the example of Atlantic grupa d.d. after the acquisition of Droga Kolinska d.d. in 2010. After the transaction, Atlantic grupa d.d. successfully operates in the food processing industry. Based on the conducted analysis, the results of the evaluation of the success of the implemented mergers and the conclusions based on the research results are presented.