The x-ray microtomography (x-ray mCT) allows investigating the internal structure of objects based on the data on the distribution of x-ray density. One of the areas of mCT researches is the investigation of the pore space of archaeological ceramics: determination of the total (microtomographic) porosity, patterns of pore distribution in the sample volume, shapes and sizes of individual pores. This work is devoted to the visualization of pores to determine the causes of macroporosity (pore diameter more than 50 nm). Large pores in archaeological ceramics are usually represented by cracks and pores that appear as a result of deviations from the technological process in the production of ceramics, pores that appear on the site of burnt organic impurities in the ceramic paste (natural or artificial), and „introduced” pores, i.e. pores in artificial and natural impurities in the ceramic paste. The latter include pores in the unburned bones, pores in the shells, pores in the grog, etc. Visualization of macropores allows in some cases to identify the burnt organic matter. For example: an unambiguous definition of a replica of a burnt seeds and fragments of the above-ground parts of the plant Panicum (Millet), Elytrígia répens, feather, wool, fragment of insect, etc. in various archaeological ceramics. So, the investigation of macroporosity by x-ray mCT gives as the additional information about environment of pottery production. This article is supported by RFBR project № 18-08-40063 and the Volkswagen Foundation, project № 90 216.