Micro-Raman is a spectroscopic technique that allows the identification of painting materials even if finely grained and mixed with others, dispersed in a binder or layered on surfaces. It is used for non-destructive, in situ measurements and it is suitable for selective studies on inhomogeneous materials or surface investigations. Some examples are described of the use of this technique in the field of art conservation and diagnostics, with regard to pigments, dyes and some products of metal alteration. Raman spectra obtained on standard painting materials were arranged in a database and published on the Web.