The paper presents the results of investigation of buckwheat flour addition to wheat flour and its effect on wheat dough rheological (alveograph) properties and on the mechanical properties of bread crumb. The results showed that buckwheat flour addition of from 10 to 40% caused a decrease of the deformation energy of wheat dough (form 248 do 91 J10-4) and of the extensibility of dough (form 89 to 21 mm), but tenacity increased. The loaf volume decreased with the addition of buckwheat flour and it had a significant influence on bread crumb texture changes. Statistically significant and negative correlations were found between loaf volume and mechanical parameters described of bread crumb texture (hardness, springiness, chewiness, gumminess). The highest changes of this parameters were observed when the percentage of buckwheat flour was 30 and 40%. Also for those percentages the lowest notes were obtained for organoleptic assessment of bread. Moreover, a number of correlations were found between the rheological properties of dough and the mechanical properties of bread crumb. The strongest and positive dependences were observed between P/L ratio (the ratio of dough tenacity to dough extensibility) and such crumb parameters as hardness, gumminess and chewiness.