Three years ago, the newly elected city council of Ghent (Belgium) committed itself to become the most child and youth friendly city of its region. For this purpose, the city council is planning a range of projects, including the design of a child and youth friendly neighbourhood on the location of a former soccer stadium. Adding the spatial dimension to political choices like this, spatial designers used to apply lists of universal child friendly design criteria, prescribing what all children and teenagers need. Child and youth studies, however, have been questioning this way of reasoning as there is no such thing like universal criteria covering the needs of all children and teenagers. Instead of planning cities for children and teenagers, they promote participation opportunities for children and teenagers in city planning. To the background of this discussion our multidisciplinary research team, consisting of researchers in social work and landscape architecture, developed a participation tool using 3D technology to involve teenagers in the planning process of a youth friendly neighbourhood in Ghent (Flanders, Belgium). Using research by design as a key concept, teenagers were not primarily asked to choose the final design but were invited to revise spatial solutions for urban challenges like housing, mobility, urban life, and public space. In this contribution we will report on the 3D participation tool and results from the workshops with teenagers.