Products containing buckwheat flour are characterized by a good nutritional value and pro-health substances contained therein as well as by a low glycemic index. Those features can be useful when designing new products containing buckwheat grains. The objective of the research study was to compare some selected properties of starch isolated from buckwheat with the features of buckwheat flour and wheat starch. It has been proved that, because the size of buckwheat starch granules is more than 10 times smaller than that of wheat starch, their properties vary widely, although the two starches have the same type of polymorphic structure and a similar content of amylose. The buckwheat starch had a higher gelatinization temperature and its enthalpy of gelatinization transition was higher than that of the wheat starch. In the case of the buckwheat flour, even higher values of gelatinization transition temperatures were recorded as were low values of swelling power and amylose leaching ability, which, likely, resulted from the presence of proteins on the surface of starch granules. Those properties affected the digestibility of starch. The starch in the buckwheat (raw) flour was characterized by a high content of resistant starch (RS); however, after it was isolated from the flour, the content of RS was insignificant and lower than that in the wheat starch. After cooking, the percentage contents of rapidly digested starch in the flour and in the isolated starch were at a similar level. After gelatinization, the content of RS was higher in the buckwheat than in the wheat starch; this fact indicated that the susceptibility of buckwheat starch to retrogradation was higher than that of the wheat starch.