The Six Sigma business strategy system is focused on quality of processes. It aims to improve quality by identifying and removing of causes of problems that lead to defects and reduces variability of business processes in production and service companies. Six Sigma concept uses different methods of quality management including statistical methods and creates specific and required infrastructure of human resources within organisation using Champions, Master Black Belts, Black belts and Green Belts which are educated in using Six Sigma methodology. Each Six Sigma project carried out within company has determined sequence of steps and is quantified with financial goals. After excellent results of implementation Six Sigma methodology in Motorola and GE have been published, Six Sigma methodology has become a popular approach in many organizations today as a concept for improving the efficiency of business processes, quality of services and products as well as concept for costs reduction. However, not all companies, that have implemented Six Sigma methodology, published excellent results. Studies have shown that more than 90% of the companies, that initiated the implementation of Six Sigma concepts within their organizations and the conducting of Six Sigma projects, failed to achieve significant cost savings that could be seen in the company's balance sheet or in the price of its shares. Such contradictory results of applying Six Sigma concept showing that the implementation is not an easy process, and that there are factors that significantly affect the implementation of methodology and the successful conduction of Six Sigma projects. In this thesis, with reference to the theory and experience in the implementation of Six Sigma, a study of critical success factors and the most significant benefits achieved in the implementation of Six Sigma concept in European companies has conducted. In order to develop a model for selecting the best Six Sigma projects in the industry, researched results have been compared with the published empirical studies to determine the key success factors, the most significant benefits and their weights.