Microwave complex permittivity measurements of activated carbons were investigated using two different microwave measurement techniques, microwave cavity perturbation at 2.5 GHz and broadband coaxial probe in the frequency range between 10 MHz and 10 GHz. Such measurements demonstrate the ability of these materials to interact with the microwave electric field, both in terms of strong polarization and absorption. We have thus used complex permittivity to quantify the variability of different forms of activated carbon produced from different sources and different treatments, such as thermal treatments or impregnation. In addition, the cylindrical cavity at 2.5 GHz was used for temperature-dependent dielectric properties measurements of activated carbons to investigate their susceptibility to microwave heating as function of temperature. Microwave complex permittivity of activated carbons was measured in the temperature range from 30?C up to 150?C.