The objective of the research was to verify the hypothesis assuming that the diversified water retaining capacity of crumb surface of wheat bakery products resulted from the addition of potato flakes or margarine during the production process. The assessment was carried out based on water vapour sorption isotherms for crumb and on selected parameters of crumb microstructure estimated using adsorption methods. The research material consisted of wheat bakery products with margarine (M) and potato flakes (Z) added. It was found that the sorption isotherms for bread crumb with added margarine and potato starch (derived from potato flakes) were characterized by a similar flow (t_cal. = 1.820, t_crit. = 2.228) within the whole a_w range. The presence of fat (derived from margarine) in the wheat bread crumb did not cause the microstructure of its surface to become significantly diversified (a_sp. = 180.4 m²/g; r_k = 2.4 nm; t.c.c. = 127.8 cm³/100 g d.m.) compared to the wheat bread crumb produced with the addition of starch (derived from potato flakes) (a_sp. = 176.8 m²/g; r_k=2.5 nm; t.c.c. = 136.1 cm³/100 g d.m.). The values of the estimated surface microstructure parameters of M and Z wheat bread crumb proved the occurrence of retrogradation of the starch fraction.