The X-ray densitometry is considered one of the main non-destructive techniques for the analysis of wood due to the high precision and practicality. The method has been applied in determining the density of the wood, and the density variation is a result of the anatomical structure and chemical composition of the same. This technique is still used in the identification of growth rings and determine the pattern of radial variation of density. This work aimed to ascertain the reliability of the information obtained by the x-ray densitometry technique in determining radial density profile on clones from Eucalyptus sp.. To this, it were used two and three clones of Eucalyptus grandis and of Eucalyptus urophylla, respectively, with 53 months of age. For radial profile of density determination, withdrew a sample, from each individual, was withdrawn perpendicularly to the axis, passing through the medulla at 1.30 m above the ground. The remainder of the radial sample was sectioned into small specimens with two millimeters of thickness, approximately, for determination of density by hydrostatic method. Analysis of the data obtained showed that the pattern of radial variation of density obtained by the technique in challenge is very similar to the standard achieved by the determination of density by hydrostatic method, inferring so that the technique is reliable for this kind of analysis.