The fraction of pore volume in AAC products covers the range from 65 to 90%. There is a set of different types of pores, e.g. large air pores are a macroscopic structural element, capillary pores and nano pores, which are connected to microstructure of the solid matrix and have specific functional effects.Different methods of pore generation and haracterization of pore size distribution are summarized. Gas producing agents, foaming agents, prefabricated foam and voluminous water retarding components are compared with regard on their suitability for AAC product properties. Image analysis, mercury intrusion porosimetry, gas adsorption porosimetry and other methods are reviewed with respect of their application for AAC material. Influence of pore size, pore shape, proportion of different pore types on related properties is presented and discussed. Homogeneity of material, isotropy of properties and range of property values with respect to porosity influences are regarded.