How do digital start-ups innovate? This is one of the main questions that the present report seeks to shed some light into. Using Henry Chesbrough's pioneering work as a starting point, the author sets out to determine how five digital start-ups from the North-East of England manage their innovation processes, and if, eventually, they practice Open Innovation. The research method that was used in the present dissertation is a multiple case study, in which the managers of all five enterprises, which consist mainly of mobile application and software developers, were thoroughly interviewed. Among the main contributions provided by this book is the adaptation of the much discussed Open Innovation paradigm to a small and medium start-up setting rather than a large and well established corporation, as has usually been the case. Furthermore, the author tackles key issues that are gaining relevance in the digital start-up sector, such as entrepreneurship, creative clusters and open sourced software.