The conversion of pronominals to copula forms is rather common cross-linguistically, and has also received a certain amount of attention in the literature, starting with LI & THOMPSON's article "A mechanism for the development of copula morphemes" (1977). The use of pronouns as copula forms has also been described for Eastern Iranian, but these data have not yet been compared to parallel patterns of other languages in the typological or general linguistic literature. So the first part of the article intends to link Iranian data investigated several decades ago with the research carried out more recently in linguistics on a great variety of languages other than Iranian. A presentation of the Eastern Ir. data will be followed by a comparison with parallel structures in other languages with view to the questions how such constructions emerge, and why languages recruit a new copula at all. The second part argues that some Western Ir. pronominal clitics might derive from copula forms or verbal endings. Here as well, the motivation of this process will be discussed.