With the advance in mobile wireless communication technology and the increasing number of mobile users, peer-to-peer computing, in both academic research and industrial development, has recently begun to extend its scope to address problems relevant to mobile devices and wireless networks. This paper is a performance study of peer-to-peer systems over mobile ad hoc networks. We show that cross-layer approach performs better than separating the overlay from the access networks with the comparison of different settings for the peer-to-peer overlay and underlying mobile ad hoc network.