Religious affiliation in Czechia and Slovakia: Comparison and regional differentiationThe dissolution of Czechoslovakia in 1993 also led to a different development of religiosity 1 in Czechia and Slovakia in the last 30 years, which, however, continued to take into account the historical conditions of the last centuries. The current state of the religious structure of the population of Czechia and Slovakia is the result of the influence of several common (both states in the EU, open borders in the Schengen area, etc.), but also different factors (different role in the relationship between the church and the state, different number of migrants from abroad, migration from Slovakia to Czechia, etc.). The paper aims to analyse the development of religiosity of the population in both states over the last 30 years and to explain the causes of regional differentiation in Czechia and Slovakia. By comparing the results of the 1991 and 2021 censuses, we have identified not only spatial disparities at the national and regional level but also the driving forces that had the greatest impact on them. Secularization tendencies on the one hand and interest in new religiosity or alternative spirituality can be observed in both countries, but in the case of Czechia it is a more pronounced acceleration.