The relevance of cloud computing is growing daily, providing a vibrant technical environment where innovative solutions and services can be created. The Cloud promises availability of cheap and flexible services for end-users and allows small organizations and individuals to host and offer world-scale services themselves.

However, while there has been substantial research and development in the field already, there still remains a large set of open challenges:

Expertise for Cloud usage is still mostly lacking, leading to unclear Cloud business models and revenue streams; interoperability issues on all levels make moving into and in particular out of the cloud difficult; software engineering paradigms do not allow for the type and level of scalability envisaged by Clouds; at the infrastructural layer, resource contention leads to unpredictable performance; resource management and scheduling is still very basic etc.

These open challenges raise a lot of the interest throughout the scientific community. To this special issue alone, 42 high quality papers were submitted, out of which we selected 4 papers (approximately 9 % acceptance ratio). The review process started on July 2013 and ended on April 2014 after two rounds of reviews by around 90 reviewers.

This special issues covers topics ranging from dynamic management solutions for service workflows and languages for policy management specification to schedulers for scientific clouds and component-based frameworks for multiple clouds application development and migration.

The contributors are Dr. Yi Wei, Dr. M.Brian Blake, Mauro Canuto, Dr. Jordi Guitart, Elina Pacini, Dr. Cristian Mateos, Dr. Carlos García Garino, Paraiso Fawaz, Dr. Philippe Merle, and Dr. Lionel Seinturier.

We would like to thank the authors of all the submitted papers for the high quality of their scientific contributions. We also thank all reviewers for their dedication and timeless efforts, which allowed us to select very high quality papers.