Citizen participation is enshrined in the Norwegian Planning and Building Act (PBA) 1985 and accentuated by the 2008 revision of the PBA. In this article, we ask if the research on participation in municipal planning is sufficient to draw conclusions on whether the Act is effective with regard to both the spirit and the letter of the law. The guiding framework for the analysis is based on the concepts of input and output legitimacy and the distinction between ‘tidy’ and ‘untidy’ participation. The analysis is based on scientific publications published after the 2008 revision of the PBA. We find that the majority of the research concentrates on zoning plans and municipality-initiated ‘tidy’ participation. As a result, there are gaps in the research with regard to both the planning context and the interconnectedness of different forms of participation. Therefore, the research reviewed can only partially inform the law-makers on the functioning of the Act.