The focus of this paper is on the methods and techniques of improving business processes as key components of every organization that operates on the market. As the goal of every organization is to perform its activities efficiently, it is also crucial to strive for optimization and constant improvement of existing processes by the demands of consumers, the market and/or stakeholders. The concept of improving business processes is not something that can be characterized as a novelty because the beginnings of business process mapping were developed at the beginning of the Japanese automobile industry (especially in Toyota) and the Japanese are responsible for a large number of methods for improving business processes. Some of the most famous methods used today are: Just in Time, Kanban, Total Quality Management, Supply Chain Management, SMED, and Six Sigma. The methodology that will be the key in this paper is called Six Sigma, which means a set of methodologies and tools used to improve business processes by reducing defects and errors in processes. Lean methodology is also associated with Six Sigma, the goal of which is to increase efficiency, which in combination makes them a powerful guide for any process-oriented organization. The goals of this paper are: (1) to describe different concepts of improving business processes, (2) to show the differences between them and how to apply them, and (3) to show, on the example of a selected business process, possible improvements by applying one of the methods. Through the analysis of different literature that focuses on the improvement of business processes and the list of methods for them, a case study will be conducted on the processes of the Faculty of Economics and Business in Zagreb as a research method. All the necessary data will be collected to determine the current flow of the business process, which will be summarized with diagrams, and potential improvements will also be shown. The example that will be used in the case study is the process of enrolling students at the Faculty of Economics and Business in Zagreb. The case study will start with the collection of data on the current process using Six Sigma methods, more specifically the SIPOC diagram, and their redesign within the framework of the methodologies mentioned earlier.