This Volume contains the 11 papers corresponding to poster and demo presentations accepted to the 7th ACM/IEEE International Symposium on Modeling, Analysis and Simulation ofWireless and Mobile Systems (MSWiM 04), that is held October 4-6, 2004, in Venice, Italy. MSWiM 2004 (http://www.cs.unibo.it/mswim2004/) is intended to provide an international forum for original ideas, recent results and achievements on issues and challenges related to mobile and wireless systems. A Call for Posters was announced and widely disseminated, soliciting posters that report on recent original results or on-going research in the area of wireless and mobile networks. Prospective authors were encouraged to submit interesting results on all aspects of modeling, analysis and simulation of mobile and wireless networks and systems. The scope and topics of the Posters Session were the same as those included in the MSWiM Call for Papers (see above). Poster presentations were meant to provide authors with early feedback on their research work and enable them to present their research and exchange ideas during the Symposium. All submissions to the call for posters as well as selected papers submitted to MSWiM 04 were considered and reviewed. The review process resulted in accepting the set of 11 papers included in this Volume. Accepted posters will also be on display during the Symposium. The set of papers in this Proceedings covers a wide range of important topics in wireless and mobile computing, including channel allocation in wireless networks, quality of service provisioning in IEEE 802.11 wireless LANs, IP mobility support, energy conservation, routing in mobile adhoc networks, resource sharing, wireless access to the WWW, sensor networks etc. The performance evaluation techniques used include both analysis and simulation. We hope that the poster papers included in this Volume will facilitate a fruitful and lively discussion and exchange of interesting and creative ideas during the Symposium. We wish to thank the MSWiM Steering Committee Chair Azzedine Boukerche and the Program Co-Chairs ofMSWiM 04 Carla-Fabiana Chiasserini and Lorenzo Donatiello for their valuable help in the selection procedure. Also, the MSWiM 04 Publicity Co-Chairs Luciano Bononi, Helen Karatza and Mirela Sechi Moretti Annoni Notare for disseminating the Call for Posters. We wish to warmly thank the Poster Proceedings Chair Ioannis Chatzigiannakis for carefully doing an excellent job in preparing the Volume you now hold in your hands.