Nowadays, technology for breast screening is mainly limited to use of 2D mammography techniques. In the developed countries, tomosynthesis has already entered in the routine examination. New breast modalities are emerging like breast Computed Tomography and phase contrast imaging. The development of new X-ray breast imaging techniques and procedures as well as their optimization stage is best studied by 3D computational breast models. This work presents the validation of a realistic software breast phantom, generated with the BreastSimulator software application [1] . The breast initially was created in uncompressed form. Generated components included glandular and adipose tissues, skin and Cooper ligaments. Subsequently, the model was subjected to compression simulation to compress the breast as it is during the mammography procedure. Then, the external shape of the model together with the breast was printed with a stereolithographic printer and filled with animal fat. The physical model was imaged both at ESRF, Grenoble and at clinical mammography unit. In parallel, the imaging procedure was simulated under the same clinical conditions by using the computational model. Simulations were carried both by Monte Carlo and analytical approaches [2] . Images obtained at experimental and simulated conditions were compared quantitatively and subjectively. A very good visual similarity is observed between the images, with an excellent visual agreement of the breast tree structure on the images. Quantitative assessment of images was also performed. This included comparison of several extracted features such as profile comparison, power spectrum and fractal dimension analyses. The validated software breast phantom is currently used in experimental work which focuses on the design of new breast physical phantoms dedicated for novel imaging techniques. This project received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No. 692097 for the MaXIMA project.