This book constitutes the proceedings of the 9th IFIP WG 8.5 International Conference on Electronic Participation, ePart 2017, held in St. Petersburg, Russia, in September 2017. The 11 revised full papers presented in this book were carefully reviewed and selected from 14 submissions. The papers reflect completed multi-disciplinary research ranging from policy analysis and conceptual modeling to programming and visualization of simulation models. They are organized in four topical threads: methodological issues in e-participation; e-participation implementations; policy modeling and policy informatics; critical reflections.