— Dissemination of common information through broadcasting is an integral part of wireless network operations such as query of interested events, resource discovery and code update. In this paper, we characterize the behavior of information dissemination in power-constrained wireless networks by defining two quantities, i.e., broadcast capacity and information diffusion rate and derive fundamental limits in both random extended and dense networks. We find that using multihop relay, the rate of broadcasting continuous stream is Θ(log(n)− α 2 ) in extended networks; while direct single-hop broadcast is efficient for dense networks. Furthermore, regardless of the density, information can diffuse at constant speed, i.e., Θ(1) in both extended and dense networks. The theoretical bounds obtained and proof techniques are instrumental to the modeling and design of efficient wireless network protocols.