The Cathedral has a number of side chapels, or chantries. These were mostly paid for by wealthy local families, so that Mass could be celebrated for their souls after they died.
The largest of the side chapels is the Lady Chapel. Others include the Coulston Chapel, now dedicated as a place of prayer for those who have lost babies during pregnancy or children in their infancy; the Whiteside chantry, dedicated as a place of prayer for the Diocese of Lancaster.
A side altar is also dedicated to St Charles Borromeo, a 16th century Italian cardinal who was patron of the local deanery at the time St Peter's was built.