Christians that follow the Orthodox tradition accounted for 61% of the population of Eastern Europe in 2010. This region has the highest percentage of Orthodox in the world (Atlas of Global Christianity, 2010). Russia has the largest number of Orthodox, as indicated by the size of the circle, with nearly 90 million adherents making up 64% of the population (Operation World). In terms of Orthodox percentage of population, Romania has the highest (87%), followed by Bulgaria (79%), Russia (64%), Ukraine (61%), Moldova (62%), and Belarus (58%).
Catholics were estimated to be 19.4% of the population in Eastern Europe (Atlas of Global Christianity, 2010) and are found in higher proportion on the western side of Eastern Europe. Poland has the highest percentage of its population that is Catholic (86% with a population of 32 million), followed by Slovakia (80%) and Hungary (60%). The largest Christian tradition in the Czech Republic is Catholicism, though making up just 20% of the population. The non-religious account for 71% of the population of the Czech Republic, the highest percentage in the world according to Operation World.