The Sustainable Urban Mobility Plan (SUMP) is a concept of the European Union. The non-binding guidelines formulated within this framework aim to help municipalities and cities to strategically define a local and long term transport and mobility plan. From the European Union's point of view, citizen participation plays a pivotal role during all phases – from the development of the plan until its implementation. This intends to achieve greater support and acceptance from the community for the plan, and to facilitate its implementation. This paper investigates whether the planning and political SUMP approach guarantees successful participatory processes, and what conclusions can be drawn to amend the SUMP process and general transport planning practice. It discusses how citizen participation is defined in the SUMP guidelines and how these elements are reflected in the SUMP guidelines of 2013 and 2019. In a second step, this paper shows how successful citizen participation is defined in an academic context and to what extent the SUMP reflects these findings. The findings derived from the academic context are then applied to the case studies of Ghent and Limburg in order to evaluate how successfully participation procedures were implemented in these SUMP processes. Finally, the question - what conclusions can be drawn from this to improve the SUMP process and general transport planning practice - is assessed. ; Der „Nachhaltige Urbane Mobilitätsplan“ (Sustainable Urban Mobility Plan, SUMP) ist ein Konzept der Europäischen Union. Die in diesem Rahmen formulierten Richtlinien dienen Kommunen und Städten als unverbindlicher Leitfaden mit dem Ziel, die lokale und langfristige Verkehrs- und Mobilitätsplanung strategisch in einem Plan zu definieren. Die Beteiligung von Bürger:innen nimmt dabei aus Sicht der Europäischen Union von Anfang an eine zentrale Rolle ein und setzt sich während der Aufstellung und Umsetzung des Planes fort. Dadurch sollen eine höhere Unterstützung und Akzeptanz für den Plan erzielt, sowie dessen ...