Peer-to-peer computing is becoming a very popular computing paradigm due to the wide diffusion of Internet file sharing applications. The growing number of mobile personal computing devices, together with the proliferation of wireless and pervasive communication technologies, also demand for the adoption of P2P paradigms in the mobile computing area. An interesting and challenging environment where P2P technologies could be employed is represented by "mobile ad hoc networks" (MANETs), which show many similarities with P2P systems. However, many of the classic assumptions that can be made for classical wired P2P systems do not hold for such environments. In order to develop P2P applications on top of mobile handheld devices, a framework, named JMobiPeer has been developed. It has been designed to work on J2ME enabled mobile devices, interacting each other in an ad-hoc fashion. In this paper we analyze the cost of its interoperability with JXTA, a well known P2P framework developed in Java, by comparing its performance with that of JXME, the JXTA prototype for mobile devices.