For archiving, art historical purposes and restoration, "two dimensional" (2-D) works of art such as paintings or photo-graphs have, in modern times, traditionally been documented using (colour) photography and/or digital imaging tech-niques. While current technology allows reproductions with high spatial and colour resolution, these techniques only document the 2-D form and colour of the surface of the object. Surfaces also have, however, three dimensional (3-D) properties which play just as important a role in determining an objects appearance and how it is perceived. Among these, surface roughness/texture and the optical properties of transparent layers are particularly important. Both determine the way light is scattered from the surface, and influence not only colour perception, but also glossiness, illusions of transparency, and depth perception. These properties are often the first to be affected before colour changes happen or are perceived in a measurable quantity. They are difficult, if not, impossible to document using current 2-D techniques, while current 3-D scanners do not have the resolution necessary to document the micro-roughness of surfaces which actually determine appearance. The Netherlands Institute of Cultural Heritage has started a multidisciplinary programme to study the effect of 3-D pro-perties of surfaces on the appearance of works of art. The combined effects of colour, roughness, and optical properties of transparent layers are being investigated in situ using standard engineering micro-roughness measurements, colour spectroscopy, and digital imaging techniques. Initial work indicates that these are excellent methods for documenting, for example, the effects of cleaning of paintings and face-mounted photographs. Combined with light scattering models, they will provide a good tool for understanding the appearance of objects, and for their conservation. Rendering models, for example, could help conservators make selections of retouching materials based on colour and texture, or varnishes based on optical properties.