Here you'll find lots of information about Sri Lankan masks.!
Sri Lankan masks are a part of the country's rich and ancient folk traditions which have still survived. They represent one of the most extensive and well-documented masking traditions of Asia. Sri Lanka has a rich tradition of masked dancing and an immense verity of intricately carved and brightly painted masks. These masks, made almost entirely of wood.

The tradition of masks that we have inherited has its origin in healing the sick. In the past, sometimes even now people are inclined to believe those super natural beings such as devils or departed souls inflict the human beings with diseases or epidemics. As E.g. GARA YAKKA mask use for protect from evil eye and mouth. The dance call Gara Yakkuma. Further they believe that by making offerings & pleasing them with ritualistic dances, such epidemics or diseases could be overcome. The Sri Lankan masks were first made for the use in those rituals. The witch doctor wears the masks made imitating the imaginary faces of the devils supposed to have caused the sickness and dances to the rhythm of the drum in the occasion of thovil ceremonies.

It has to be stressed that in Sri Lanka the masks have no religious value of religious connotation. It is not connected with Buddhism and it is true that the masks are part of Thovil or Devil dancing, the rituals performed to heal the sick. But are should not rush to conclusion that there is a Buddhist value in mask, simply because the Buddhist villagers seek the assistance of Thovil, where masks are used.