Dielectric properties and structure of pure and carbon-modified nanocomposites on the base of porous glasses with an average pore diameter of 6 nm (PG6) with embedded KNO₃ have been studied at the temperature diapason of 300–430 K and at frequencies of 0.1–3 × 10⁶ Hz on cooling. X-ray diffraction studies of these samples have shown, that in modified and unmodified composites there is a mixture of the low-temperature paraelectric phase ($\alpha$-phase) and the ferroelectric $\gamma$-phase. In modified composites, a decrease in permittivity and conductivity is observed. Dielectric response has been analyzed in the framework of modern theoretical models. Two relaxation processes have been identified and their origin has been determined. It has been found that the main contribution to the dielectric response of nanocomposite material PG6+KNO₃ is provided by charge polarization on interfaces, which can be governed by modifying the inner pore surfaces. DC-conductivity of both composites has been estimated and the activation energies have been determined. Activation energy change observed in a vicinity of 360 K is attributed to the phase transformation and the appearance of KNO₃$\alpha$-phase.Dielectric properties and structure of pure and carbon-modified nanocomposites on the base of porous glasses with an average pore diameter of 6 nm (PG6) with embedded KNO₃ have been studied at the temperature diapason of 300–430 K and at frequencies of 0.1–3 × 10⁶ Hz on cooling. X-ray diffraction studies of these samples have shown, that in modified and unmodified composites there is a mixture of the low-temperature paraelectric phase ($\alpha$-phase) and the ferroelectric $\gamma$-phase. In modified composites, a decrease in permittivity and conductivity is observed. Dielectric response has been analyzed in the framework of modern theoretical models. Two relaxation processes have been identified and their origin has been determined. It has been found that the main contribution to the dielectric response of nanocomposite material PG6+KNO₃ is provided by charge polarization on interfaces, which can be governed by modifying the inner pore surfaces. DC-conductivity of both composites has been estimated and the activation energies have been determined. Activation energy change observed in a vicinity of 360 K is attributed to the phase transformation and the appearance of KNO₃$\alpha$-phase.