ENThe article analyses the internal differentiation of the Kaunas subdialect of the Western Aukštaitian of the Lithuanian language. Based on the phonetic features in the maps of the Lithuanian Language Atlas (“Lietuvių kalbos atlasas”), the dialect areas of Kaunas are defined and the importance of the features determining them is evaluated, basing the results on the objective methods of instrumental phonetics (“Praat”) and quantitative dialectometry (“Gabmap”). The hierarchical model of the dialect features of the Kaunas subdialect stands out from other Lithuanian subdialects. Due to its closeness to the standard language, the nomenclature of the features of the Kaunas subdialect only formally corresponds to the correlation mentioned in the works of dialectology with Johan Taeldeman’s (2006, 233–248) trinary structure because the main distinguishing and characteristic features of the subdialect basically coincide with the equivalents of standard language, and so they are not identified as dialectal by ordinary language users. Therefore, both when distinguishing the entire regiolect of southwestern Aukštaitian from other dialectal units, and when differentiating the inner areas of the Kaunas subdialect, the importance of weak, or tertiary, dialectal features become particularly evident.Instrumental and dialectometric research confirmed that in the area of Western Aukštaitian of Kaunas at the beginning of the 21st century not only quantitative but also qualitative properties of vocalism become important. As weak features acquire more differential power, not only the relevant (usually stressed) but also irrelevant (usually unstressed) positions of vowel phonemes become significant. Keywords: Lithuanian dialects, Western Aukštaitian of Kaunas, phonetics, dialectal differentiation, dialectal feature. [From the publication]