Public and stakeholder participation in environmental planning is often assumed to enhance effectiveness through improving the environmental quality of decisions and enhancing implementation. We draw on the literature on participatory environmental governance in order to derive key participation-related factors that are hypothesized to impact on decision quality and implementation. We then outline four cases of decision-making processes in local environmental planning in Germany, representing a variety of forms of public participation, and what we suggest can be seen as four different pathways to ‘success’ in participatory planning. The case studies, recounted on the basis of stakeholder interviews and secondary research, are subjected to a cross-case analysis in order to examine the influence of participation in each case. We consider how key participation-related factors played out across the cases, and assess both decision quality and implementation against counterfactual non-participatory, or less-participatory, scenarios. In moving beyond accounts of ‘what happened’, and considering how participation changed the order of things relative to ‘what would have happened’ under different scenarios, the research highlights how very different pathways may lead to ‘success’ in participatory environmental planning from the viewpoint of process organizers and planners sympathetic to environmental issues. We conclude that, given the significance of context and surprises, planners and process organizers must be open to different pathways to the successful conclusion of participatory planning processes.