Abstract Latvian and Lithuanian share a large number of related lexical items in their standard varieties, but even more so in their dialects. Even though the traditional regional dialects are relatively well-preserved both in Latvia and Lithuania, nowadays they are disappearing. For this reason, a project called Atlas of the Baltic languages was initiated in 2006, with the aim to study both Baltic languages from a geolinguistic point of view. Altogether, five volumes are planned for the Atlas of the Baltic Languages, presenting the dialectal vocabulary in thematic groups: flora-related vocabulary; fauna-related vocabulary; human physical qualities and kinship terminology; housing and settlement; natural phenomena, time, weather, etc. The selection of the lexical items for the Atlas of the Baltic Languages is based not only on words of common origin in Latvian and Lithuanian, but also on related semantics, therefore all volumes will include semantic maps as well.