Message from the Chairs It is our great pleasure to welcome you to attend the third ACM International Workshop on QoS and Security for Wireless and Mobile Networks (Q2SWinet 2007). This year's Q2SWinet continues the tradition of previous successful workshops: ACM Q2SWinet 2005 in Montreal, Canada, and ACM Q2SWinet 2006 in Torremolinos, Spain. The workshop provides a wonderful forum for the discussions and presentations of original ideas, recent results and achievements by researchers, students and system developers working on the issues related to QoS and Security for Wireless and Mobile Networks from different technological perspectives. The mission of the workshop is to give researchers and practitioners a unique opportunity to share their experiences and ideas with others. This opportunity is enriched by the fact that Q2SWinet 2007 is to be held in conjunction with MSWiM 2007 (the 10-th ACM/IEEE International Symposium on Modeling, Analysis and Simulation of Wireless and Mobile Systems) in the same venue. You are cordially invited to submit your original papers within the submission deadline (i.e., June 1st, 2007). Submission is now open in EDAS and submission instructions are available in the Q2SWinet 2007 website. With the help and dedication of Technical Program Committee members and peer reviewers, papers of the highest quality will be selected in order to ensure an outstanding technical program. The workshop proceedings will be published by the ACM Press, and will appear on the ACM Digital Library by including both regular papers and extended summaries of the poster session papers. In addition, we are pleased to announce that a Special Issue of Wiley's Wireless Communications and Mobile Computing (WCMC) Journal will contain a revised and extended version of selected papers originally presented at Q2SWinet 2007. We do hope that you will contribute to this workshop with various ways to make it a great success. Come to join us in the Q2SWinet 2007 to enjoy its wonderful technical program as well as sunny and beautiful Crete Island, Greece! Hsiao-Hwa Chen Q2SWinet 2007 General Chair National Sun Yat-Sen University, Taiwan     Luciano Bononi Q2SWinet 2007 Program Chair University of Bologna, Italy