As a large number of studies have reported, one of the most important problems in the restoration of polychrome surfaces with laser-cleaning techniques is colour alteration. A comprehensive examination of the object to be cleaned is required. It should include a well-researched history of the object and a serious analysis of the original materials, as well as those used during past restorations (repainting, chromatic integration, etc.). The chemical compositions of the pigments from different periods and from different schools of restoration are varied and have individual responses to the laser irradiation. New materials used in painting embrace a large territory, especially in large outdoor paintings. Their behaviour in laser-cleaning treatment must be known in advance for various applications - painting cleaning, chromatic integration, graffiti cleaning, etc.