Porosity in the hardening system consists of air cells, which are the main element of the cellular concrete structure and that formed when gas emission in the mixture or during the foaming. The paper presents the developed models of porous structure formation in autoclaved aerated concrete (AAC) and foam concrete (FC). We elaborated the concept of bubble porosity in fresh concrete by distinguishing three types of bubble pores: microbubble pores, membrane pores and cellular pores. The sizes of such pores are determined and the possibility of pore shape deformation is evaluated. The study revealed that capillary and hydrostatic pressure are the essential factors in the process of bubble system formation. Reducing the size of deformable cellular bubbles and obtaining an increased number of non-deformable membrane bubbles improves the AAC and FC structure. This is a promising method of improving AAC and FC production technology.