Although public participation is recognized as a cornerstone of Canadian environmental assessment processes, it is unclear to what degree that involvement influences the outcome at the various stages. This review, undertaken as part of the participation of Ontario Nature and Environment North in the Panel Review of the Marathon PGM-CU Mine Project, provided an opportunity for an investigation into the efficacy of public comments on influencing the Environmental Impact Statement Guidelines of various past panel reviews. The purpose was two-fold. Firstly, the investigators wished to determine what types of comments had been made in previous assessments in order to determine if they had had some effect. Secondly, they wished to use this information to inform the comments they would put forward in the Marathon project.