As carbon nanotubes (CNT) and graphene nanostructures (GNR) constitute the basis of high-speed nanoelectronics and nanosensors, we examine the fundamental properties of various CNT-metal (Me), GNR-Me, and CNT-graphene interconnects. The cluster approach based on the multiple scattering theory as well as effective medium approximation were used to model the dispersion law, electronic density of states (DOS), and conductivity, etc. Multiple scattering problems were solved for nanostructures with radial (quantum dots) and axial (nanowires, nanotubes) symmetry. Interconnect capacitances and impedances have been evaluated in the GHz and THz regimes. Parametrical numerical simulations of conductivity were carried out for zig-zag (m,0) , armchair (m,m) , and chiral (m,n) CNTs, and the sensitivity of conductivity to the local electronic DOS in CNTs with local impurities (N and B atoms) was demonstrated. CNTs, CNT-Me, and GNR-Me based nanostructures are prospective nanosensor structures.