Kostanjski families are Croats and they are mostly from Zapresic area. In the past century, relatively most of Croatian residents bearing this family name were born in Zapresic area and in Zagreb. In Kraljev Vrh in Zapresic area every eighth inhabitant had the family name Kostanjski.
Prevalence
About 100 people with faimily name Kostanjski live in Croatia today, in 40 households. There were 100 of them in the middle of the past century, and their number remains constant. They are located in four Croatian counties, in 7 cities and 10 other places, mostly in Zagreb (45), Jakovlje in Zapresic area (40), Matenci (<10), Glavnicica (<10), and in Kraljev Vrh in Zapresic area (<5).
Outside Croatia
At least one family with this surname emigrated from Croatia to the United States. Family name Kostanjski is present in two countries.
In the sources analysed in the project Acta Croatica so far, the name is mentioned few times, the first time 1906 in source Yearbook and Directory of Literary Society of St. Jerome 1906.