Specific, with respect to their treatment during incineration, are the medical and electronic solid wastes because of their chemical composition different from the municipal solid wastes. Although existing methods of thermal incineration of those specific wastes are safe and environmental-friendly, the problem of disposals of those fly ashes and recovery of deficit elements such as gold, copper, heavy metals or rare elements from them is still unsolved. Plastics, derived, for example, from packages, cause additional emission of chlorine compounds, dioxins, furans, or heavy metal compounds, which are added as colorants or PVC additives. Properties of fly ashes collected from dust removal devices installed in a medical waste incinerator, electronic waste incinerator, and after an installation for dangerous wastes utilization (HCB contaminated soil) in rotary drum furnace have been compared in this paper