Over the past fifty years, various complex interdisciplinary diagnostic plans have been implemented in Italy during the execution of conservation projects on stone sculptures and on large bronze sculptures. Within this framework, radiographic examination techniques have been increased. The radiography, a non-destructive methodology that considers the work of art at the macroscopic level, has maintained a central role within the diagnostic phase, both for the purpose of reconstructing the ancient art techniques and procedures and to evaluate mechanical and structural aspects.  The history of studies is presented, considering the different radiographic methodologies: use of medium-energy X-rays, high-energy X-ray applications (linear accelerators), use of gamma radio-isotopic sources (gammagraphy).  The study describes the results achieved in important cases in the history of stone and bronze sculptures, among which the case study of the equestrian monument of Marcus Aurelius assumes particular relevance. The essay also describes the first application of “high-energy X-rays” involving the Majesty Group of Orvieto Cathedral, which is composed of the Madonna and the Child, two groups of angels and a bronze canopy. The concluding part of the essay defines the methodological criteria necessary for the correct interpretation of the results, in particular, with regard to the radiographic examination of the bronze sculpture, the correlation between the information derived from that examination and the casting procedures, with particular consideration of the casting defects and discontinuities.