The ratio of the α-decay widths of a bare nucleus and the related atom is calculated. Both the change of the form and thus the penetrability of the potential barrier and the effect of reflection in the classically-allowed region appearing due to the electron shell are taken into account in the calculations of this ratio. The contribution of each of these two effects is of one and the same order of magnitude. For long-lived radioactive samples the values of the total effect turn out to be somewhat below 1 percent.