This book constitutes the refereed proceedings of the 15th International Colloquium on Structural Information and Communication Complexity, SIROCCO 2008, held in Villars-sur-Ollon, Switzerland, in June 2008. The 22 revised full papers presented together with 2 invited talks were carefully reviewed and selected from 52 submissions. The papers cover topics such as distributed algorithms, compact data structures, information dissemination, informative labeling schemes, combinatorial optimization, and others, with potential applications to large scale distributed systems including global computing platforms, peer-to-peer systems and applications, social networks, wireless networks, and network protocols (such as routing, broadcasting, localization).