Abstract. Ontology reuse saves costs and improves interoperability between ontologies. Knowing which ontology to reuse is difficult without having a quality assessment. We employ user ratings to determine the user-perceived quality of ontologies. The combination of an Open Rating System (ORS), user ratings, and information on trust between users, allow us to compute a personalized ranking of ontologies. In this paper, we present our extension, the Topic-Specific Trust Open Rating System (TS-ORS). To overcome the limitations of the ORS, the TS-ORS features topic-specific trust and multi-faceted ratings. In a user study, we show that having user ratings and result ranking based on a TS-ORS significantly facilitates ontology assessment and selection for the end user.