In the literature on civil conflicts, federalism is often touted as a useful institution to address regional demands. However, diversity in the groups present in a country is also associated with a higher tendency for conflicts. In this article we examine how the geographic distribution of groups across a country affects the ways in which federalism contributes to conflict resolution. Of tantamount importance in assessing these effects of federalism is whether particular types of distributions of groups across a territory make the adoption of federal institutions more likely. We find federal countries with strong ethno-federal arrangements to be particularly conflict-prone.