ENIn the past Zarasai region was at the cultural borderline. Before the foundation of the Lithuanian state, the region was on the frontier of two Baltic cultures - two territorially defined cultural identities that were in close neighbourhood for a long period - Selonians and Lithuanian tribes. The images of these tribal relations have permeated our recent historical thinking: Lithuanian tribes were aggresive fighters and fearful participants of successful and unsuccessful attacks, while Selonians - cowards hiding in forests and passively accepting the imposed conditions. Despite obvious differences between the stereotypes of Selonians and Lithuanians, those weapon co-holders and allies (noted by K. Būga), they were considered as tantamount companions. According to historical sources of the middle of the 13 th century, terra Selo- nia was the object of territorial division between the Order and Mindaugas, who has already possessed Selonia at that timedisposition. Historical sources do not clarify under which circumstanes Selonia went to Mindaugas. It is considered to be a result of friendship between Selonians and Lithuanians, and it ended in ethnic and later - political assimilation of Selonians. As noted by some linguists, Lithuanian people has populated Selonia since the 7th century and mixed with them. Bearing in mind the fact that since the 15th century the Selonia land disappeared from regional and political maps, it should be asserted that this friendship led to the loss of Selonians identity. The article evaluates the relations between Selonians and Lithuanians on the basis of theory, which admits that social interaction was the main factor for the emergence of ethnic and cultural boundaries. Cultural differences exist not due to isolation and long distance or poor communication in remote and deserted locations.on the contrary, cultural differences can emerge only through intense relations between adjacent cultural groups, which treat each other as different and stranger entity. What relations according to archaeological sources did the Lithuanian and the Selonian tribes maintain in the past: friendly or hostile ones? The article analyses archaeological sources of burial monuments (the size of burial barrow cemeteries, mounds, the number of graves and their constructions, body treatment, burials of horses), which let us admit that cultural differences as regards Žiemgaliai (Semigallians), Aukštaičiai (Samogitians) and Latgaliai (Latgalians) were not as vivid as between Sėliai and Lithuanian tribes. This type of cultural diversity along the the Šventoji River has remained unchanged since the middle of the 1st millennium and was stable for about 600 years. In the middle of the 1st millennium Lithuanian approached the Šventoji River but did not cross it; instead of it, communities moved to the east towards these lake areas: Dusētai, Samavas, Luodis, Šventas, Dūkštas and Smalvas. Archaeological data do not provide any information on “Lithuanian” monuments in the territory of Selonia. Moreover, even these scarce features, which tended to be linked to to Lithuanian rites (e. g., human cremations, burial of horses) are not of “Lithuanian” style. It should be noted that there is no evidence that in the 7th-12th centuries Selonia would be inhabited by Lithuanians and this fact denies the statements about the early assimilation and lituanization of Selonia.It is difficult to unambiguously interpret the differences in burial customs prevailing in Lithuania and Selonia: despite the fact that relationships between both communities were frequent, this did not result in cultural uniformity; on the contrary, it helped to reveal completely diverse identities. Having lived in the neighbourhood for many ages they acted as strangers, though there are no direct signs of hostility, which could turn into military conflicts. In the 12th century, the situation changed and great changes emerged in the territory of Sėliai; this occurred concurrently with military political activities of Lithuanian tribes.