The mechanism of reinforcement (enhancement of elastic modulus) of nanocomposites with elastomeric matrix by carbon nanotubes was considered. It has been shown that interaction of matrix polymer and carbon nanotubes leads to formation of interfacial regions having high modulus of elasticity. This effect defines the enhancement of modulus of elasticity of polymer matrix, modified by action of nanofiller in comparison with the same characteristic for matrix polymer. This circumstance leads to reduction of real reinforcement degree of nanocomposites polymer/carbon nanotube in comparison with nominal one. The usage of real values of reinforcement degree of nanocomposites allows its correct description within the frameworks of the very various models: mixtures rule, micromechanical and percolation ones. The estimation of real values of elastic modulus for nanofiller aggregates and interfacial regions demonstrated their large (by several orders of magnitude) difference from nominal characteristics of these parameters for initial nanotubes and matrix polymer. The stiffness of polymer matrix exercises decisive influence on real value of elastic modulus of carbon nanotubes in polymer matrix of nanocomposite. This circumstance leads to approximately the same ratio of elastic moduli of carbon nanotubes aggregates for nanocomposites with elastomeric and glassy polymer matrix. The necessity of using dynamical model (with application of real characteristics of polymer matrix and carbon nanotubes) for correct description of structure and properties of nanocomposites polymer/carbon nanotube is general conclusion of the present work, whereas static models, using nominal values of the indicated characteristics, given tactless results.