Abstract: For conservation of the built cultural heritage the application of conservation products like consolidants or water repellents is often used. A natural stone is, however, a complicated heterogeneous porous system making the process of consolidation dependent on many variables. The selection of a suitable consolidant and consolidation conditions therefore remains a complex issue. The impregnation depth is a key factor for the assessment of the treatment efficiency. So far, the methods used for monitoring the penetration depth usually require a cut of the investigated stone. These destructive approaches, however, significantly reduces the number and choice of the investigated cuts. The methods, furthermore, do not allow dynamical studies of the impregnation process. The combination of state-of-the-art hybrid pixel semiconductor detectors with newly available micro-focus X-ray sources makes X-ray radiography an ideal non-destructive tool for the penetration depth monitoring. In this contribution, we present results of high-resolution X-ray radiography applied for the penetration depth monitoring of polymer consolidants in the Opuka stone.