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%.
Religion in Ukraine
In the 10th century the emerging state of Kievan Rus' came increasingly under the cultural influence of the Byzantine Empire. The first recorded Rus' convert to Eastern Orthodoxy, the Princess Saint Olga, visited Constantinople in 945 or 957. In the 980s, according to tradition, Olga's grandson, Knyaz (Prince) Vladimir had his people baptised in the Dnieper River. This began a long history of the dominance of Eastern Orthodoxy in Ruthenia, a religious ascendancy that would later influence both Ukraine and Russia. Domination of Little Russia by Great Russia (from 1721) eventually led to the decline of Uniate Catholicism (officially founded in 1596) in the Ukrainian lands under Tsarist control.