Discussions around two related concepts of “diaspora” and “irredenta” do not subside, but acquire a new sound in the global world, in which significant disintegration processes are taking place. Equating terms into a synonymous series as well as their substitution lead to theoretical errors in the study of ethnic groups that have negative consequences in real life. In the article, based on a critical understanding of modern discourses of diaspora and irredenta, the common features and distinctive features of key concepts are analyzed. In it, using the example of two types of ethnic groups, the variability of ethnic and national identity, loyalty to the country, attitude to the territory of residence, as well as the ethnic network and connections with co-ethnics on different sides of the interstate borders of the two are studied. Particular attention is paid to the threats and risks associated with separatist and secessionist sentiments in the irredenta, which, unlike the diaspora, claims the original residence in the border, disputed territories. The findings and recommendations may have implications for practical work in the field of ethnic policy and university education.