While members of regional and ethnic minorities can reach the highest echelons of power, in most contexts they remain politically marginalized and under-represented in formal politics. The heterogeneity of regional and ethnic minority groups creates a challenge for the study of representation if one wants to avoid the traps of essentialism and unrealistic assumptions. The inclusion of regional and ethnic minorities in legislatures and government can increase trust, alleviate conflict, and provide substantive representation. Much evidence shows that, on average, representatives of regional and ethnic minorities work in the name of their respective groups, especially in ‘low-cost’ activities like asking parliamentary questions. Such substantive representation should be the guiding principle, but the relationship between descriptive and substantive representation seems moderated by the context in which legislators operate.