This paper proposes a context-dependent case-based mechanism for selecting negotiation partners with the focus on the adaptation of similarity relations to a specific context. The similarity relations are important part of the reasoning mechanism and have to be defined in a way consistent with the specific type of interaction, the negotiation. We validate the proposed approach with the use of both the probability and possibility distributions by performing experimental evaluation. Categories and Subject Descriptors I.2 [Artificial Intelligence]: Learning, Problem Solving General Terms Algorithms, Theory Keywords possibility theory, case-based reasoning