Differentiation has become a core feature of EU integration. However, we still know little about how citizens evaluate differentiated integration (DI). What kind of DI is appreciated by which kinds of citizens? A particular focus of the article is on the evaluation of institutional design. Are there standards of procedural fairness shared by citizens across different EU member states? Or, is support for different forms of DI conditional on whether and how a citizen’s member state is affected by DI? The article draws on newly collected data on citizens’ attitudes towards DI, including a conjoint experiment conducted in eight EU member states, to get a better understanding of what drives support and opposition to different forms of DI.