Eastern Ukraine
According to a 2016 survey of religion in Ukraine held by the Razumkov Center, 73.5% of the population in Eastern Ukraine were Christians (63.2% Eastern Orthodox, 8.1% simply Christians, 1.0% Protestants, and 0.3% Latin Rite Catholics), 0.5% were Muslims, 0.3% were Jewish, and 0.3% were Hindus. Not religious and other believers not identifying with any of the listed major religious institutions constituted about 24.7% of the population. It also showed that approximately 55.6% of the population of eastern Ukraine (which in Razumkov's mapping excluded Donbass and consisted of the regions immediately to the west of it) declared to be believers, while 13.4% declared to be undecided or non-believers, and 3.5% declared to be atheist. 
A 2007 survey by the Razumkov Centre asked "Would you like to have your region separated from Ukraine and joined another state?" In eastern Ukraine, 77.9% of respondents disagreed, 10.4% agreed, and the rest were undecided. 
In a poll conducted by the Kyiv International Institute of Sociology in the first half of February 2014, 25.8% of those polled in East Ukraine believed "Ukraine and Russia must unite into a single state", nationwide this percentage was 12.5%.
Wołyń Voivodeship (1921–1939)
The primary religions practised in the area were Eastern Orthodox Christian (69.8%), Roman Catholic (15.7%) as well Judaism by the Jews (10%), Protestantism (2.6%) and the Islamic faith by the Tatars. With respect to the Orthodox Ukrainian population in eastern Poland, the Polish government initially issued a decree defending the rights of the Orthodox minorities. In practice, this often failed, as the Catholics, also eager to strengthen their position, had official representation in the Sejm and the courts. With time, some 190 Orthodox churches were destroyed or disassembled (many of them already abandoned), and 150 more were transformed into Roman Catholic churches. Such actions were condemned by the head of the Ukrainian Greek Catholic Church, metropolitan Andrei Sheptytsky, who claimed that these acts would "destroy in the souls of our non-united Orthodox brothers the very thought of any possible reunion."