The paper presents the results of an investigation into the effect of the type of activating agent on the formation of the microporous structure of activated carbon monoliths obtained by chemical activation involving calcium chloride, phosphoric(V) acid, and zinc chloride. The research into the microporous structure of the activated carbon monoliths subject to the analysis was based on the innovative method of porous structure analysis along with the unique fast procedure of multivariant identification of adsorptive systems. The analyses carried out with the use of the mentioned method were based on nitrogen, carbon dioxide, and methane adsorption isotherms. The research evidenced that a microporous structure analysis based on various adsorption isotherms and involving the method in question yields comprehensive and reliable information on the adsorptive properties of analysed materials, which is useful for technologists and designers alike.