Last name Sidjak (Sidjak 
, Сидяк 
) , in the world, is a rare family name. The family name Sidjak is habitual in Eastern Europe, particularly Ukraine, where it is a rare surname, Belarus, where it is a very rare surname, and Russia. Not in comparison with a country's population, it is commonest in Ukraine, Russia, and Canada. Much less frequently, Sidjak is the forename as well as the last name.