To meet the growing energy demand and thereby increase power-generating capacity, the dependency on coal for power generation, are required a more environmentally friendly methods of fly ash utilization. Therefore, the priority is to characterize domestic fly ash in detail in order to ascertain its potential uses as raw material in the production of high-value products. The high silica content of fly ash makes it a potential useful source for the synthesis of nanoporous materials, such as zeolites and mesoporous molecular sieves. The physicochemical properties of fly ash coming from seven coal-fired power plants and three heat and power plants in Poland are presented in this work. The fly ash was sampled from power plants that use combustion of lignite and hard coal in pulverized-fuel boilers (PC) and circulating fluidized bed (CFB) boilers. The fly ash was examined for its morphology, chemical and mineral composition, grain size, structure and thermal stability by using advanced instrumental techniques (XRF, XRD, SEM, BET, TGA). According to mineralogical and chemical composition of fly ash, three fly ash samples are potentially useful as a raw material for making zeolite A, two samples for zeolite X and fly ash No. 8 for zeolite Y. The samples with the highest content of SiO₂ and Al₂O₃ (Nos. 2-6 and 9) can be used to synthesize mesoporous molecular sieves such as MCM-41 and SBA-15. Received zeolites and mesoporous sieves from these fly ash samples will be used for removing NO₂ from exhaust gas, and these studies can be implemented in power plants with CO₂ capture, in the process of exhaust gas purification to removal of NO₂.