This book constitutes the thoroughly refereed post-conference proceedings of the 4th International ICST Conference on Personal Satellite Services, PSATS 2012, held in Bradford, UK, in March 2012. The 22 revised full papers presented together with 4 poster sessions were carefully reviewed and selected from various submissions. The papers cover topics such as radio resource management; spectrum/interference management and antenna design; mobility and security; and protocol performance in satellite networks.