This book constitutes the proceedings of the First International ICST Conference, MOBILIGHT 2009 held in Athens, Greece in May 2009.The 40 full papers presented focus on topics such as WPAN, WLAN, WMAN/cellular as well as architectures and design methodologies to support seamless access to the comunication facility. Further contents are services, in the vison of "always on" requirements as well as business models, oportunities and solutions.This volume reflects the current request for lighweight, wireless communication devices with high usability and performance able to support added-value service in a highly mobile environment.