Data Protection is of extremely high relevance these days. The fast progression technological development leads to a massive digitalisation of data, which makes data much faster and easier accessible. Furthermore, new business models with a technological background have emerged, which was not foreseen not even two decades ago. One of these business models is Cloud Computing. Cloud computing is ubiquitous. For example in the US, small enterprises is said to increase from 37 to nearly 80 percent until 2020. In the UK in 2014 already 75 percent of the SMEs used cloud services in some way, the number for bigger enterprises is probably even higher. Germany, however, falls behind in numbers, only 44 percent of the businesses using Clouds in 2014. These numbers are still speaking for themselves: cloud computing is already of high importance in business and will in all probability be growing in the future, due to the fact that amongst others, it can safeguard expenses and facilitate especially international commerce and trade. Clouds are furthermore not exclusively used professionally. The non-business use of Clouds in Norway for example, amounts for instance to 43 percent, followed by Iceland (39 percent) and Great Britain (38 percent). In the European Union clouds are used on an average of 22 percent. These numbers might be smaller than in fields of business but cannot be expected as a sign for decreasing numbers of use in private cases. Cloud computing will therefore be of particular importance both in professional and private fields in the future. Since Cloud Computing is a model completely dependent on technologies, it is also imperilled to dangers accompanied by technology. Failures of servers or networks are as well possible as the system can be hacked by people. Due to inherent dangers, it is essential to also have security measures available – therefore data protection law is necessary. This book is supposed to serve as a handbook on cloud computing that on one hand should give people who are not very familiar with technology a short and easy understanding of cloud computing itself. On the other hand it is supposed to also explain the main legal bases that are important for cloud computing, including the new data protection rules of the EU. These new rules contain two different instruments of which only one is directly important for cloud computing: the new European Privacy Regulation. The Data Protection Directive for the police and justice sector however does not affect Cloud Computing immediately and will therefore be excluded in this title.