In Croatia, Kostrenčić families are almost entirely Croats (from Crikvenica ), barely Italians (from Rijeka ). In the past century, relatively most of Croatian residents bearing this family name were born in Rijeka and Crikvenica.
Prevalence
About 60 people with faimily name Kostrenčić live in Croatia today, in 40 households. There were 30 of them in the middle of the past century, and their number doubled. They are located in four Croatian counties and four other places, mostly in Crikvenica (35), Zagreb (10), Dubrovnik (<10), Rijeka (<5), and in Pula (<5).
Outside Croatia
At least one family with this surname emigrated from Croatia to the United States. Family name Kostrenčić (including: Kostrencic , Costrencich ) is present in 8 countries worldwide.
In the sources analysed in the project Acta Croatica so far, the name is mentioned over twenty times, the first time 1902 in source Hartmann's General List of Apartments in Zagreb.