In Croatia, Kostecki families are generally Croats (from Novska area ), very rarely Ukrainians (also from Novska area ), and . In the past century, relatively most of Croatian residents bearing this family name were born in Kutina and in Novska area. In Donja Vlahinička in Kutina area every fiftieth inhabitant had the family name Kostecki.
Prevalence
About 40 people with faimily name Kostecki live in Croatia today, in 15 households. There were 40 of them in the middle of the past century, and their number remains constant. They are located in threee Croatian counties, threee cities and four other places, mostly in Lipovljani in Novska area (20), Kutina (<10), Popovaca in Kutina area (<5), Zagreb (<5), and in Repusnica (<5).