A new measurement system of dielectric permittivity and loss tangent of ornamental stones used for example on historical buildmgs has been developed Complex permittivity has been measured in the frequency range 1.1 - 1.7 GHz on samples chosen between marbles, sandstones and limestones. The values of dielectric parameters were measured experimentally by placing the sample in a resonant cavity obtained from a waveguide. The research has been developed to define a laboratoy testing method in order to improve GPR interpretation by creating a data base of electromagnetic properties of the analysed materials.