Non-destructive and quantitative investigation of density distribution of round tablets was the objectives of this study. The density distribution of round tablets was observed using X-ray computed tomography (X-ray CT). The distribution images were visualized by fractionating the CT images into 25 unit cells and averaging the CT number for each cell. The profiles of the distribution were analyzed with respect to the compression pressure by partial least squares (PLS) method. Analysis using the PLS method resulted in regression and loading vectors depicting the contribution of the change in density due to the variation of compression pressure. The vectors were also composed of 25 positions and used to reconstruct density mapping. The reconstructed maps quantitatively indicated the regions reflecting changes in density. At the upper and lower surface of tablets, increasing the compression pressure increased density in the edge region and decreased density in the center region. The center region under the upper surface was weakly affected by the pressure change. These results well agreed with the simulation results of finite elemental method. We suggest that the effects of compression pressure visually revealed in each region of the tablet by the X-ray CT and PLS methods are generated by density imbalance resulting from high pressure compression. (C) 2016 Elsevier B.V. All rights reserved.