Carbon nanotubes effectiveness, as thermally conductor, in polymer/CNTs nanocomposites, is related to main aspects as dispersion, interfacial thermal resistance and thermal contact resistance. Features of raw materials and processes parameters for the realization of nanotube/polymer composites, can affect simultaneously the above critical issues, also in adverse way. In this contribution, polypropylene based-composites, containing multi walled carbon nanotubes (MWNTs), are prepared by melt-blending and then characterized prevalently in term of thermal transport behavior, choosing different matrix grades, filler functionalization and process conditions. In more details, the influence on properties of products of both two commercial polypropylene resins, different in MFI and the addition of a compatibilizer, as maleic anydryde grafted polypropylene (Ma-g-PP), is verified. Moreover, three different commercial MWNTs with the same aspect ratio, one neat and two chemically modified with carboxyl –COOH and amino –NH2 groups, respectively, are chosen to prove effects of functionalization on thermal conductivity of nanocomposites. Finally, different melt-compounding and molding conditions in terms of temperature, time, screw speed, pressure, filler drying and so on, are considered to optimize them for enhanced thermal conductivity.