The Cathedral of Saint Lawrence in Lugano, Switzerland is an important religious and historical site that contains both immovable and moveable works of art. Although the structure itself has changed, it retains many important wall paintings. In 1910, the cathedral underwent comprehensive restoration under the direction of Augusto Guidini and the painter Ernesto Rusca, including executing new paintings on undecorated surfaces, adding decorative features such as frames to some existing paintings, and retouching and filling losses to create a harmonious and coherent scheme in which all phases remained legible. By 2000, conservation issues were evident for all painted surfaces, including efflorescence, flaking paint and losses. From 2009 to 2017 another restoration project was carried out. The conservation of the wall paintings proved to be a complex process and two main aspects were important in informing decisions regarding methodology and treatments: the effects of moisture and climate, and the role of the unifying decorative scheme from the Guidini/Rusca intervention. The success of the recent project rested on prioritising the conservation needs of the paintings, considering the changes necessary to satisfy the religious and public function of the building, and wrestling with the historical, ethical, and material issues connected with the earlier intervention.