This article is a theoretically oriented contribution seeking to review the existing literature directly or indirectly addressing the “diversity gap” in political parties. Within this particular field I identify two main areas to conduct research: participation and representation. The premise is that the particular features of political parties, given their role in the democratic system, implies that they cannot be neutral when they identify the diversity gap as a problem, and therefore have to follow some strategies to deal with it. Based on the literature review and by preparing the theoretical framework of the different case studies for this Special Issue, I propose an interpretative framework comprising four main channels of potential analysis. I will end by arguing that what all these studies highlight is that in dealing with the incorporation of immigrants into political parties, the utilitarian logic prevails over any argument based on equality and power sharing.