In this study, two polyamides were used: one with greater chain flexibility, polyamide 6.6 (PA6.6), and another with two benzene rings in the main chain, poly (hexamethylene isophthalamide-co-terephthalamine) (aPA), to evaluate how the structural factor influences on rheological behavior of nanocomposites with carbon nanotube (CNT). The rheological behavior was investigates using linear viscoelastic measurements in oscillatory shear with small strain amplitudes. For all nanocomposites, the store (G’) and loss (G’’) moduli increase at all frequencies with increasing CNT loading. Different behavior on G’ curve was observed. A tendency of G ' to present a behavior independent of frequency (formation of a plateau) for PA66 nanocomposites was observed. In this case, the entanglements and/or the nanoparticles play the role of temporary junction zones and can be indicative of the formation of a three-dimensional network. On the other hand, for aPA a nonterminal low-frequency rheological behavior has been observed, that could be related that most of the polymer chains in these composites are tethered to the surface at one end and hence cannot relax.