Large migratory movements that followed after Sutamarský peace (1711) in Hungary significantly changed the ethnic structure of its population. They included also migration of Slovaks to present-day Romania Bihor area. This colonization process took place in several waves since the late 18th to 19th century, supported by the Hungarian aristocracy. In contrast to the settlement of fertile lowlands in "Dolná zem" (Lower Country) the motivation of migration were land use of mountain Plopis, located in Bihor in northwestern Romania. Article deals with the problem of the origin of the Slovak population in Romania Bihor in the context of the work of Romanian linguist and Slovakist - Grigore Benedek, with respect to the language.