This paper presents the results of the study on the determination of the effect of measurement depth on the value of flesh firmness for apples of McIntosh, Spartan and Starkrimson varieties. It was found that the depth of measurement had a significant effect on the value of flesh firmness. The firmness measurement error, caused by the differences in plunger penetration depth of 1-3 mm, may reach values from 3.1 up to approx. 15 %.