International regimes, defined as sets of norms and rules around which members’ expectations converge, are providing structures for facilitating cooperation in a given issue area. Two main lines of environmental regime scholarship prevailed thus far: one on structural design aspects of international institutions and one on their effects and effectiveness. However, questions on how such effects are achieved in detail largely remain unanswered. Against this background, this study aims to analyze the institutional design conditions under which regional regimes produce strong or weak policies. We do so by qualitatively comparing, using a fuzzy-set Qualitative Comparative Analysis (fsQCA), nine regional regimes across the world towards their ability of producing regime forest policies as an illustrative issue area. Three structural conditions were identified as being influential on regime policy: (i) The degree of formalization (ii) The existence of hegemonic/powerful member state(s) and (iii) Scope or issue specificity bearing the identity of a regime. Our results showed that no one condition on its own was necessary to produce either strong or weak regime forest policy. However, all three conditions, through three different configurations, created a robust pathway for producing strong regime policy. In addition, the combination that showed the presence of all three conditions was related to weak regime policy. These results open several prospects for future research on the relationship between regimes´ structures and regime policy.