Dujak families are Croats and they are mostly from Bosnian Posavina. In the past century, relatively most of Croatian residents bearing this family name were born in Bosanian Posavina (Odzak area) and in Bosanian Posavina (Bosanski Brod area).
Prevalence
About 210 people with faimily name Dujak live in Croatia today, in 90 households. There were 20 of them in the middle of the past century, and their number multiplied. They are located in the most of Croatian counties, in 17 cities and 31 other places, mostly in Slavonski Brod (65), Zagreb (25), Osijek (15), Rijeka (<10), and in Vinkovci (<10).
Outside Croatia
Family name Dujak (including: Dulyak , Dujack and Dujac ) is present in 16 countries on four continents. "Dujack " is used by some 50 people in the United States.
In the sources analysed in the project Acta Croatica so far, the name is mentioned few times, the first time 1902 in source Hartmann's General List of Apartments in Zagreb.