In this article we present to the Czech reader for the first time the concept of verticalism or linguistic verticalization as a process of language shift and language change, first introduced by the linguists Salmons (2005) and Frey (2013). The theory aims to clearly describe the transition of self-government functions on the community level into the hands of a superior political entity. In our case, we approach it primarily from a sociolinguistic point of view, where the community is represented by a minority language and the specific superior political entity by a majority language. We applied this verticalization theory in a very interesting area: Western Asturian-Leonese languages, Mirandese and Leonese, which are spoken in Portugal and Spain. Although these languages are genetically very closely related, each of them is at a different stage of a co-officialization process, which is involved in determining the degree of verticalization. Field research in the described areas yielded results based on the experience of bilingual speakers as reported in questionnaires and interviews that completed the final picture of the ongoing verticalization process.