This work reports a statistical study on the relationship between the chemical–physical properties of CNTs, which vary by changing the conditions of purification and plasma treatment, and the macroscopic properties of PC-based nanocomposites. CNTs are synthesized and then purified in two different ways and used as fillers for the preparation of PC/CNTs nanocomposites. In some cases, oxygen plasma treatment is carried out to improve their affinity to the matrix. The CNTs are characterized by TGA, ICP/OES, and FT-Raman spectroscopy, titration and morphological analysis. Mechanical, dynamic-mechanical, electrical, and morphological tests are used for characterizing PC/CNTs nanocomposites.