The author presents theoretical and practical problems related to research on linguistic diversity in the Lubuski region situated in the historic German-Polish borderland which up to 1945 belonged to Germany. After World War II, almost all of the population was replaced. Only few autochtons remained, and the area was repopulated with ethnically diverse groups of forced settlers from territories incorporated into the USSR and displaced from the Ukrainian-Polish borderland, as well as by voluntary settlers from various Polish regions. It led to creation of a complex linguistic situation characterised by, i.a., Polish-German bilingualism and the presence of the transferred East Slavic and Polish dialects.