The interior of the parish church of the Holy Trinity at Byszewo, and especially the altars from the chapels (the one on the north side was consecrated in 1762, the one on the south side in 1776) with their iconography and Cistercian reminiscences, has inspired the writing of this article. Based on an analysis of various representational and decorative motifs, it consists of suggestions that combine statements of historical fact and interpretative commentary. Although the two altars, which are part of the original project, are contemporaneous with the rest of the church interior, their form is rather distinctive. They represent the traditional type of architectural altar with columns, a sarcofagal mensa, and a tripartite retabulum which provides a background for the sculpted group in the centre. The altar on the north side depicts "The Virgin Mary with Child Handing Over Rosaries to St Dominic and St Catharine of Siena", while the one on the south side shows "Christus Ecce Homo and Cistercian Monks Presenting Arma Christi". Both altars have a simple composition and modest iconographic programme. The construction of the former may be connected with the activities of the Rosary Brotherhood, the latter with the Chrząstowski Family. In her interpretation, the author highlights the way in which the two chapels express thetwo main traits of Cistercian piety, Christocentrism and the Marian cult. The altars are a fit complement to a programme, devised by the local Cistercians. It was a programme which bundled together the three functions of the building, that of a parish church, a Marian sanctuary and a church commemorating the original Cistercian foundation and housing the bones of the dead monks.