The statements of historians working on several selected regions in the Slavic region (from the Middle Ages to the 20th century) will serve as cases study to reflect on the main problem: ‘Slavdom as a broadly understood frontier society’ .The Slavdom was/is a mosaic of religion, ethnic groups, cultures, traditions. It is a world, where a sense of unity (the idea of a Slavic community) meets with a strangeness and otherness (divisions among Slaves and among another group living in the Slavic world). The Slavdom in itself is divided by the border between two European Christian traditions (Catholicism and Orthodoxy). Another characteristic feature is the fluidity of the borders to all sides. This provoked (and still does) the status of a cultural borderland on the whole region. A key for a research on the issue of Slavdom borderlands will be: a language as a medium of culture and identity. A language can work as an including- but also as an excluding-element within a society – like a basis to a build up a ‘we’-community or to distinguish from a ‘they’-group. A level of good/bad communication defines as well the level of closeness between people. Therefore, we would like to investigate processes of acculturation, assimilation, different forms of coexistence (e.g. living physically together but nonetheless separately, forms of cooperation etc.), and conflicts caused by language-groups (also ethnic, social etc.) on the Slavdom greater region. The diversity of cultural factors and constant encounter with ‘otherness’ created a characteristic atmosphere of the great borderland and encouraged an influx, exchange and development of diversity cultural patterns.