This study adopts the mixed method research design to investigate the interaction between libraries and library users on Facebook. The research objectives are: (1) To find out the performance of Facebook as a tool for interaction between libraries and library users; (2) To find out the differences in using Facebook to interact with library users between libraries in two regions: English-speaking countries and Greater China; (3) To find out the differences between academic and public libraries in using Facebook to interact with library users; (4) To find out the challenges for libraries in using Facebook to interact with library users. The study finds that quality interaction between libraries and users, like conversations and group networking, is still relatively rare on Facebook. Libraries in English-speaking countries seem more sophisticated in using this tool than their counterparts in Greater China, regarding the diversity of usages of Facebook, and the identification of the main audience on Facebook and their interests. Differences also exist between academic and public libraries, in the respects of the characteristics of user groups on Facebook and the usages of Facebook. Several challenges for libraries using Facebook are also identified, which are related to aspects of privacy, administration and the tool itself.

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