In Croatia, Olšak families are Croats (from Orahovica area ). In the past century, relatively most of Croatian residents bearing this family name were born in Pozega and Pleternica.
Prevalence
About 30 people with faimily name Olšak live in Croatia today, in 8 households. There were 10 of them in the middle of the past century, and their number tripled. They are located in only five naselja i to in Ovcare in Orahovica area (10), Pozega (<10), Pleternica (<10), Duga Resa (<5), and in Mitrovac in Orahovica area (<5).