<strong>Purpose: </strong>The aim of this study was to implement, validate and apply a tool for the assessment of the MTF and NPS of dental CBCT scanners using up-to-date measurement methods. <strong>Methods:</strong> The MTF was calculated using the circular edge method, and the NPS as the 2D Fourier transform of homogeneous background ROIs. The validation framework has been set-up as follows: images with known MTF/NPS are simulated, and from these images the MTF/NPS was calculated and the results compared. The influence of the phantom dimensions and the CNR on the MTF/NPS accuracy has been studied for a 10x10 cm<sup>2</sup> system FOV and corresponding voxel size of 0.25 mm<sup>3</sup>. For the practical measurements, two specific phantoms have been designed, based on the simulated results. <strong>Results:</strong> For the MTF the minimum number of slices needed to achieve an error of at most 5 % has been studied as a function of the CNR of the phantom rod insert (26 mm diameter). For the NPS, the number of 128x128 ROIs needed to achieve an error of at most 5 % have been determined. Measurement results on two different dental CBCT scanners for a selection of imaging conditions are presented. Conclusion: The simulation results provide guidelines for proper use of the developed tool to obtain accurate MTF and NPS measurements in practice. From the actual measurements it can be concluded that sometimes more information about system design parameters from the manufacturer is needed in order to explain the results with absolute certainty.