Over the last years, Cloud Computing has evolved to an alternative or an extension of the in-house IT infrastructure. Benefits are greater flexibility and lower costs in the medium term though resource usage that is adapted to the respective demand. There are different technical realisation of Cloud Computing depending on the application: Infrastructure as a Service (IaaS), Platform as a Service (PaaS) und Software as a Service (SaaS), with a decreasing dependency of the user (or customer) regarding the hardware actually used by the Cloud service provider. Furthermore, Clouds are distinguished between so-called public Clouds (commercial offerings), in-house Clouds (which may be operated by the local IT department or a commercial provider), hybrid Clouds that combine both types, and community Clouds that are operated by and for a dedicated community. However, there are a number of not yet fully solved matters. In particular, these concern Interoperability, Security (vendor lock-in), Data Protection, Service Level Agreements and Software Licence Management. In several national and European funded projects Fraunhofer SCAI has developed approaches addressing these matters and has acquired expertise, which we offer to our customers and partners.