This thesis deals with the topic of cloud computing, including the consideration of its essential safety and security aspects. At the end, there is an evaluation of a selected number of cloud providers regarding precisely those aspects. The first chapter is devoted both the general, technical and legal foundations of cloud services, while in the second chapter the catalog of requirements of the Federal Office for Security in Information Technology (BSI) is described. After that, certain feasible (more and less widespread) cloud solutions are assessed and rated. Cloud computing has a great growth potential and may lay the foundation for a fundamental shift in the entire IT and economic sector, as the saving possibilities will attract especially new startup companies for not having to buy expensive IT infrastructure. From the resulting popularity, a diverse, hardly manageable market to cloud providers developed. The present work provides the transmission of knowledge to evaluate various cloud services, regarding IT-security aspects, to choose the ideal provider.