The thesis investigates the potentiality of the use of Public Participation GIS methods (PPGIS) to engage people in planning processes in the Nordic context. The active participation of citizens is discussed in planning literature since long, but in practice it is difficult to achieve and to assess the role of participation in planning processes. The questions remain if public participation is itself a goal of democracy in planning practice, in which way participation is useful to achieve better, fair or just processes and what benefits can be achieved though participation. In the last decade, these questions have been discussed in parallel with the advancement of technology. This thesis looks specifically to the PPGIS method as it makes use of technology to accelerate the communication between citizens and public authorities. PPGIS represent nowadays a possible turn in the management of the participation itself, with a potential to involve easier and faster citizens in public policy. The opinions of citizens also in relation to participatory budgeting have been proven to be meaningful through PPGIS tools. However issues of public participation and the active part of citizens in the co-design of planning processes seem not all solved. The thesis investigates the PPGIS planning experiences occured in the Nordic countries specifically, where these technologies have been tested and advanced in recent years. The case studies here explored will be the master plan for the city of Helsinki (Finland) (2018-2020) and the work-in-progress adopted by Kristiansand (Norway) (2020-now) to concretise the compact city ideals. Identifying benefits and shortcomings of the PPGIS approaches, the aim is to highlight how this technology is facilitating the interplay between professionals and the citizens in the co-design and co-management processes of innovative urban solutions, paving the way for a more organic implementation of these digital tools in the planning process.