This Special Issue consists of extended versions of selected papers from the 2nd Joint IFIP Wireless and Mobile Networking Conference (WMNC 2009), held on September 9−11,2009, and hosted by Gdansk University of Technology, Poland. It was a successful attempt by IFIP WG 6.8 to merge three series of conferences: MWCN (Mobile and Wireless Communications Networks), PWC (Personal Wireless Communications), and WSAN (Wireless Sensor and Actors Networks) into a universal forum for discussion between researchers, practitioners, and industry representatives involved in the development of wireless, mobile, and sensor networks. And nowadays more than ever, there seems to be a lot to be involved in. While admiring spectacular achievements in wireless communications that have recently changed our lives in so many ways, we realize that the rapid evolution of wireless systems comes with a price tag—the pursuit of increasing functionality, reliability, availability, security, and service diversity implies design and standardization challenges that our research community is now facing. Among these challenges, distribution of multimedia contents over QoS unfriendly environments, coexistence of heterogeneous wireless technologies within unlicensed bands, exploration of underutilized wireless spectrum under the cognitive radio paradigm, self-organization, cross-layer protocol optimization, uncooperative behavior, making ad hoc and mesh networks deliver on their early promise, convergence of telecommunication and contextrich web services, and exploration of beyond GSM/UMTS concepts like 3GPP Long Term Evolution (LTE) are just a few. As novel wireless network architectures are invented