Before 990 A.D. belarusians (several eastern slavic and baltic tribes, mostly Kryvichi and their branches, Jatviags, Lits) were pagans. They believed in the God of Sun - Yaryla, celebrated seasons of nature according to sun and moon calendar. The cycles of folk songs that were sang at these celebrations still exist.
Belarusians have always been tolerant to other religions. Perhaps, it is so because they always lived on the boundary between paganism and Christianity, as it was in the X century when the Prince of Kiev decided to convert Belarusians to the “true faith”; between the Orthodoxy and Catholicism, as in the times of the Great Lithuanian Principality and Rzecz Pospolita; between the faith and atheism during the era of the USSR.