Diagnosing and understanding the properties of concrete structures allows its use in more effective ways that neither compromise application nor impose safety risks or waste materials. Several tests can be performed for this purpose, differing with regards to diagnostic precision, complexity of execution, costs, need of specific apparatus, and others. Specifications from standards must be followed to assure the durability of concrete structures, such as Eurocode 1 (EN 1992-1) and EN 206 in Europe. This study determined the volume and the distribution of pores of four concrete compositions with distinct water/cement ratio, cement consumption, and compressive strength, through tests of mercury intrusion porosimetry (MIP) and 3D microtomography. Results showed high correlation coefficients between the tests for assessing voids and compressive strength. Comparatively, the 3D microtomography test presented linear relation to the specifications of mixtures, although MIP indicated discrepancies for mixture 2.