jats:titleAbstract</jats:title> jats:pIntroducing a symposium on the question of what difference international commissions of inquiry (COIs) make, this article frames the debate methodologically and theoretically. COIs have become a common feature of responses to issues of international concern. While aspects of their work have received substantial scholarly attention, less is known about the concrete, case-specific effects of past COIs. This symposium therefore encourages empirical research into the consequences of COIs, absent or present, intended or not. After discussing some of the common challenges to the empirical research required, this framework article sets forth a non-exhaustive typology of ways in which COIs could end up making a difference, such as inspiring further action or substituting for such action; justifying decision-making, ex ante or ex post; fostering a shared narrative or hardening competing narratives; legitimizing some groups while delegitimizing others; enhancing political dialogue or intensifying division; spurring reform or encouraging more of the same; promoting (international) law or exposing its limitations. This typology is presented as a resource for hypotheses not only for this symposium but also for future empirical research into the differences made (or not) by COIs.</jats:p>