This document presents a comparison of the conservation state of the most relevant phenomena in the vowel system of the Pasiegu Dialect, spoken in some valleys of Central-Eastern Cantabria, in Northwestern Spain. We do so by taking Penny’s (1969) model and comparing it with data from two groups of present-day speakers, the most conservative speakers and the most conservative school-age speakers. The interview has two parts, a directed conversation and a linguistic questionnaire; the former searches for different various phenomena, while the later is focused on the henomenon known as vowel metaphony, characteristic of some Asturleonese dialects. This /ndocument includes the first qualitative date from the conservation interview as well as qualitative and quantitative data from the linguistic questionnaire, both showing a rapid retreat of most dialectal features, replaced by Castilian Spanish.