Recently there has been an increasing deployment of content distribution networks (CDNs) offering hosting services to Web content providers. CDNs deploy a set of surrogate servers distributed throughout the Internet and replicate provider content across these servers to provide better performance and availability than centralised provider servers do. Problems regarding robustness, scalability, accessibility and efficiency however, brought the attention to peer-to-peer (P2P) architectures for use in CDNs. In P2P architectures, every node acts as a client and as a server. This way, intelligence is spread over the network, making self-organisation and automatic recovery more easy. In this paper, we present several replica placement algorithms (RPAs) for peer-to-peer CDNs. We will show that they enhance CDN performance by determining the optimal location of content replicas on the surrogate servers.