The viscoelastic properties of several multicomponent materials (including both particulate multipolymeric materials and multilayer polymer blends) were investigated in relation to their microstructures and phase-property dependencies. Theoretical considerations based on mechanical modeling were used to explore the origin of additional mechanical transitions in experimental viscoelastic spectra. The major part of this work was devoted to particulate multicomponent systems, and especially to the further exploration of the characteristics of the so-called micromechanical transition (MMT). Although such an additional phenomenon is clearly explained as a result of a specific interphase, our investigation also provides evidence that the occurrence of a MMT in dynamic mechanical spectra reflects the contribution of the geometrical arrangement into phases of a set of properties of the pure components, rather than a molecular relaxational process within the interfacial area. Finally, on the basis of an equivalent approach, the influence of the geometrical arrangement of phases on the viscoelastic response of multilayer polymer blends was pointed out as a relevant argument to justify the existence of "spurious" additional damping peaks in some experimental dynamic mechanical spectra reported in the literature.