Surname Demcuk (Demcuk 
) , across the world, is a very rare last name. The cognomen Demcuk is habitual in Lithuania, where it is a rare surname, Czechia, and the United States, where it is an extremely rare surname. Much less frequently, Demcuk is the forename as well as the last name.
| VARIANT | COUNTRY |
|---|---|
| Demcuk | Czechia, United States, Lithuania |