This paper describes a system called Mapster that allows users in a P2P network to share their databases. The research addresses problems of heterogeneity and scalability of sharing databases in P2P networks. Fine-grained access to users? databases is provided through schema matching and a super-peer topology. The schema matching component allows information to be translated across heterogeneous databases by semi-automatically determining the mappings between the databases within the P2P network. The super-peer topology provides a suitable environment for the schema matching and query processing.