There is no doubt about the spatial accuracy of CBCT; however, to repeat the scanning for monitoring purposes, the exact position cannot be maintained. It is important to test the repeatability of CBCT measurement, especially in determining the quality of bone. A series of CBCT scanning with different angles have been carried out on a phantom, with the known densities to measure the effect of different angles on CBCT reading. Repeatability density measurement based on CBCT was also conducted on several patients to see the consistency of the tools available on commercial software. Finally, the validation of density estimation based on CBCT data is also provided in this chapter. Density has a logarithmic relationship with greyscale obtained from CBCT with an accuracy of 95%. Comparison validation using a CT scan on the same phantom showed that the density also has a logarithmic relationship with HU obtained from a CT scan with an accuracy of 93%.