The frescoes cover the entire walls of the chapel, located in the basilica's bypass. They show scenes related to St Stanislaus (whole-wall fields: Resurrection of Peter, Death of St Stanislaus), as well as figures of saints and blesseds, mainly Polish; in the arcade arcades groups of angels holding ribbons of the litany. Captions of scenes and figures in Polish.

In 1899, Tadeusz Popiel won a competition whose conditions included study of Italian Renaissance painting. Popiel therefore spent a year in Florence, Rome and Venice; in Loreto he worked on fresco technique alongside the influential German religious painter Ludwig Seitz. Completed in 1900, the frescoes in Padua - the first major church work by Popiel, hitherto known for his historical paintings and panoramas - were enthusiastically received; the painter subsequently received many religious commissions from Poland, as well as several in Italy (including co-decorating the Dutch chapel at San Antonio in Padua). Despite his studies of the patterns of Italian frescoes, the paintings represent the stylistics of realistic history painting of the second half of the 19th century, characteristic rather of oil paintings, such as those of Popiel's teacher, Władysław Łuszczkiewicz, from Kraków. The conventional character of Popiel's decorations is typical of religious art of the time in many countries, especially Italy. Only the fields with angels, as well as the ornamental elements betraying the taint of Art Nouveau, seem close to the formal artistic experiments in wall polychromy appearing in the Kraków school at the time.

The chapel contains several epitaphs and plaques commemorating Poles from different eras. The ensemble awaits scientific examination and study, and the Popiel paintings also in terms of their place in the European religious art of the time.

Since 2012, the chapel has been subject to conservation work, completed in 2018.