The ACM Conference on Recommender Systems (RecSys) is the premier annual event on research and applications of recommendation technologies. This adjunct proceedings bundle the descriptions of posters that are presented in RecSys 2017 (http://recsys.acm.org/recsys17). 45 papers were submitted to this track, with 23 of them accepted after peer-reviewing. The posters present late-breaking research results and speculative or innovative work in progress. We are grateful to the reviewers for their support. We thank all authors who submitted articles to this poster track.