Participation of citizens and organised interests in political and administrative decision making is widely perceived as an important means to enhance the effectiveness and legitimacy of public environmental governance. Yet, these claims are not uncontested and lack a sound empirical basis. With this contribution we address some of the important questions around the implications of public participation in environmental decision making. We present early results of a larger meta-analysis on 71 published water-related case studies, each of these coded independently by three researchers using a comprehensive, theoretically informed coding scheme. Statistical analysis shows a positive relationship between the employment of participatory processes and the acceptance of environmental decisions. The findings further suggest that open, information-intensive procedures positively influence the environmental standards of policy outputs. Here, particularly the environmental preferences of stakeholders serve as an important predictor for process outputs.