The aim of this master's thesis is to analyze the linguistic divergence at lexical level along the state border between southern Dalmatia and southern Herzegovina. It is based on an empirical study of vocabulary diversity and it shows a short analysis of phonetic and also morphological variability analysed by means of a questionnaire that contains approximately 90 different words and expressions. The region of research is a very fertile area of the Neretva river valley, which has remained underresearched in question of vocabulary diversity so far. The places in which the study was carried out are almost neighboring places, which are divided by the border crossings Doljani and Gabela Polje and which make this micro-region almost unique in the linguistic sense. Those two border crossings, which belong to South Herzegovina, are situated at the opposing sides of the Neretva River. The selected vocabulary of Blace, Opuzen, Metković, Kula Norinska and Zažablje was collected and analysed in southern Dalmatia region. It is very interesting to observe whether these border crossings are also linguistic border crossings. I have investigated this question by collecting and analyzing lexical data that varies in different local varieties provided by local speakers belonging to different age groups.