The possibility to classify pathological tissues – for example tumor neo-angiogenesis pattern-, using new X-ray imaging technique (such as Quasi-Monochromatic Multi-Energy X-ray Imaging) is strictly related to an accurate knowledge of their X-ray absorption coefficients μ(E). Unfortunately, tissues μ(E) values are studied and known only for a little number of pathologies and are typically obtained via mathematical analysis, such as Monte Carlo simulations. So, an experimental study of the tissue attenuation properties was started in order to investigate, define and classify not only different organ tissues, but also parameters that probably exalt differences between normal and neoplastic tissues. In particular, X-ray attenuation curves of biological tissues are measured with an experimental setup based on a Bragg monochromator - to produce quasi monochromatic X-ray beams in the range 10-90 keV - and a CdTe detector to collect attenuated X-ray spectra. To investigate tissues characteristics, different analysis methods are implemented, starting from algorithms that can extract chemical-physical information from X-ray absorption easurements, such as effective atomic number and electron density. Our results are then compared with previously published values for normal (both experimental and theoretical) and carcinoma tissues, to test the potential usage of the X-ray characterization and classification between pathological and normal tissues.