Prior to the Reformation, the Polish nobility were mostly either Roman Catholic or Orthodox with a small group of Muslims. Many families, however, soon adopted the Reformed faiths. After the Counter-Reformation, when the Roman Catholic Church regained power in Poland, the nobility became almost exclusively Catholic, despite the fact that Roman Catholicism was not the majority religion in Commonwealth (the Catholic and Orthodox churches each accounted for some 40% of all citizens population, with the remaining 20% being Jews or members of Protestant denominations). In the 18th century, many followers of Jacob Frank joined the ranks of Jewish-descended Polish gentry. Although Jewish religion wasn't usually a pretext to block or deprive of noble status, some laws favoured religious conversion from Judaism to Christianity (see: Neophyte) by rewarding it with ennoblement.

What two religions were most common?