This article explores the influence of scientific knowledge in rule-making processes to enhance environmental protection in Swedish and Norwegian forestry. It examines the mapping and protection of small reserves; the development of plans for protection of large reserves; and rule-setting in voluntary forest certification schemes. The analysis shows that Sweden has enacted more stringent environmental protection policies on all measures examined. Whereas variation in the state of knowledge about environmental protection needs does not explain these differences, variation in the access to the science-policy dialogue and in the distribution of costs and benefits in the forestry sector does help explain the differences in the stringency of Norwegian and Swedish forest policy. I conclude that the influence of knowledge depends on the process by which it is created. Although scientific information usually has little influence when strong economic counter-forces are involved in the decision-making process, this problem can be ameliorated by facilitating processes of coproduction of knowledge among scientific experts, practitioners, and decision-makers.