For heterogeneous polymeric systems obtained on the basis of polyethylene glycol and containing multi- layer carbon nanotubes as a filler, we consider the behavior of composites in temperature and ultrasonic fields at a frequency of 0.4 MHz. It is shown that the viscoelastic properties of these materials depend on the content of carbon nanotubes, temperature, and the linear sizes of structural formations participat- ing in the dissipative processes. High-molecular compounds are often characterized by specific viscoelastic properties caused by the struc- ture of the materials (1). Moreover, they exhibit the properties of both elastic bodies and liquids (2). The com- prehensive analysis of the viscoelastic properties of polymers and, hence, their structural features, can be per- formed by using the acoustic methods. Thus, in particular, the data on changes in the velocity and absorption of the stress waves enable us to directly observe the relaxation processes, study the properties of heterogeneous polymeric systems (HPS) in broad temperature ranges, and investigate the effects of structure formation and their kinetics under the action of various factors (3). The investigations carried out within the region of ultrason- ic frequencies prove to be especially promising because the relationship between the structure of a polymer and its viscoelastic properties (moduli of elasticity and internal friction) manifests itself in this case most completely (4). The results of recent investigations demonstrate that the structure of polymers can be especially intensely and purposefully changed with the help of nanoparticles among which an especially important role is played by carbon nanotubes (CNT) (5). It is shown that the presence of CNT in the HPS based on polymethylmethacrylate (2), polystyrene (1), polypropylene (3), and other compounds (5) affects the properties of materials. However, at present, the researchers focus their attention mainly on the possibility of purposeful changes in the acoustic properties of polyethylene glycol (PEG) with the help of CNT. This can be explained by the fact that systems of this sort are now extensively used for the practical purposes (6). The aim of the present work is to study the influence of CNT on the viscoelastic properties of PEG by using elements of the theory of molecular acoustics (7). The behavior of HPS containing 0-1.0 vol.% CNT is ana- lyzed by the dilatometric method and according to the temperature dependences of the modulus of relaxation and damping decrement.