This book constitutes the refereed proceedings of the 9th European Conference on Case-Based Reasoning, ECCBR 2008, held in Trier, Germany, in September 2008. The 34 revised research papers and 5 revised application papers presented together with 3 invited talks were carefully reviewed and selected from 71 submissions. All current issues in case-based reasoning are addressed, ranging from theoretical and methodological issues to advanced applications in various fields such as knowledge discovery, similarity, context-awareness, uncertainty, and health sciences.