On the extension of the main nave there is a presbytery with a post-council altar. It is decorated with stained glass windows mainly depicting the figure of St. John the Baptist. There are stellar vaults above the nave. In the western part of the central nave there is a choir with organs. From the north side, a sacristy is added to the presbytery, and the chapel of the Mother of God to the main body. The northern aisle is covered with rib vaults. The walls of the nave are decorated with polychromes. There is also the Crucifixion Group and plaques dedicated to: Bl. Sr. Jerzy Popieluszko, card. Stefan Wyszyński and card. Józef Glemp and Archbishop Józef Kowalczyk. In the northern aisle there is an entrance to the crypts.
In the southern aisle there are two side altars: the Heart of Jesus and St. Joseph. Like the northern aisle, it is covered with rib vaults and polychromes. On the walls of the southern aisle there are plaques dedicated to Fr. Sińcki and Bishop Jan Bernard Szladze.