ungarians (Magyars; see Hungarians in Romania), especially in Harghita, Covasna, and Mureș counties, and the Roma are the principal minorities, with a declining German population (Banat Swabians in Timiș; Transylvanian Saxons in Sibiu, Brașov and elsewhere), and smaller numbers of Czechs, Slovaks, Serbs, Chinese, Croats, and Banat Bulgarians (in Banat), Ukrainians (especially in Maramureș and Bukovina), Greeks of Romania (especially in Brăila and Constanța), Turks and Tatars (mainly in Constanța), Armenians, Russians (Lipovans, Old Believers in Tulcea), Jews and others. Since the Romanian Revolution of 1989, Bucharest has again become an increasingly cosmopolitan city, including identifiable Chinese and Irish presences. Minority populations are greatest in Transylvania and the Banat, areas in the north and west of the country, which were part of the Kingdom of Hungary (after 1867 the Austria-Hungary) until the end of World War I. Even before the union with Romania, ethnic Romanians comprised the overall majority in Transylvania. However, ethnic Hungarians and Germans were the dominant urban population until relatively recently, while Hungarians still constitute the majority in Harghita and Covasna counties.
Reference 1: number and %.
Reference 2: Romanians, Hungarians, Germans, Jews, Ruthenians and Ukrainians, Russians, Bulgarians, Rromi, Turks, Gagauzians, Czechs and Slovaks, Serbs, Croats and Slovenes, Poles, Greeks, Tatars, Armenians, Hutsuls, Albanians, Others, Undeclared and Total.
Source: http://en.wikipedia.org/wiki/Demographics_of_Romania
Reference 2: Romanians, Hungarians, Germans, Jews, Ruthenians and Ukrainians, Russians, Bulgarians, Rromi, Turks, Gagauzians, Czechs and Slovaks, Serbs, Croats and Slovenes, Poles, Greeks, Tatars, Armenians, Hutsuls, Albanians, Others, Undeclared and Total.
Source: http://en.wikipedia.org/wiki/Demographics_of_Romania