This book constitutes the refereed proceedings of the 10th International Conference on Electronic Commerce and Web Technologies, EC-Web 2009, held in Linz, Austria, in September, 2009 in conjunction with Dexa 2009.

The 31 revised full papers presented together with 2 invited papers were carefully reviewed and selected from 61submissions. The papers are organized in nine topical sessions on e-payments and trust, domain knowledge and metadata exploitation, design and modelling of enterprise and distributed systems, electronic commerce and web 3.0, collaboration-based approaches, recommender systems modelling, reputation and fraud detection, recommender systems and the social web, and recommender systems in action.