The aim of this work is to analyse the microstructure variations of sand packings during vibrations by X-ray tomography. X-Ray tomography is a non destructive technique providing 3D information on the microstructure of materials. It is becoming very attractive to study granular packings. Mathematical morphology tools are used to analyze the packing fraction, the size distribution in the sand and in the porous phase. Axial and radial dispersion are also analyzed. At first, image analysis is used to check the homogeneity of the packing fraction of our initial state before vibrations. Then loose and dense packings after vibrating have been compared using the intercepts distribution in the sand and in the porous phase. Effects of compaction and expansion due to vibration on packing characteristics are discussed from the results.