The space housing the Diocesan Museum of Monreale, a Museum of Christian art that represents the faith and devotion of the Diocese in time, is on three levels in the Archbishop's Palace.
The first, on the ground floor, has an access corridor that holds stone material coming from various parts of the Diocese, and leads to the San Placido Hall, with a spectacular opening onto the Benedictine cloister. The great hall, in addition to its large walls for large altarpieces, offers exhibition space for the grandiose tapestry depicting the famous theme of  William's Dream, and in special showcases placed on the walls that ideally reunite the side altars is space for the exhibition of some different types of alter panels, almost coeval to the paintings.

The first floor has two rooms. These host the oldest works of the Diocese, both with stunning views of the gulf of Palermo. The first room faces the inside of the Cathedral, offering a prestigious view of the mosaics, and brings back a chronological order by grouping works of art from the Norman period, continuing to the second room where there are works from the sixteenth century. It also gives a privileged close-up view of the polychrome exterior decoration of the Cathedral's apses.

On the second floor, in two large adjoining halls, the museum exhibition offers a path that develops the history of the Diocese through enlightened bishop patronage. The hall displays the wallpapers and furnishings commissioned by the Archbishops who succeeded one another in time and overlooks the cloister, giving the visitor a unique view from above. The final section of the hall, with its barrel-vaulted painted ceiling commissioned by Archbishop Domenico Gaspare Lancia di Brolo, in Monreale from 1884 to 1919, is home to the later works, a selection of objects of particular artistic interest.
It was necessary to separate the diocesan works from those donated by Salvatore Renda Pitti, maintaining the homogeneity of the original collection in an isolated exhibition that is located before the hall dedicated to the Bishops. The exhibition of the collection, through the selection of the most artistically interesting artifacts in their variety, with the added privilege of Christian works of art, provides a significant example of private collections that, through donation, go to public use.

Still on the second floor in a separate area is an anthropological section that brings together works of devotional nature.
The Crucifix Chapel in the Cathedral of Monreale is part of the exhibition itinerary; it was commissioned by Archbishop John Roano, head of the Diocese from 1673 to 1703. Enhancing the already precious baroque Tempietto coffer, all the works of art commissioned by the Spanish High Bishop are displayed, thus maintained in the original location they were made for.