The results of studies of the break-up of deuterons in the field of nuclei with different masses are reviewed. The data obtained in kinematically complete experiments are analyzed within the diffraction model. It is ascertained that the differential cross-section of the deuteron break-up non-monotonously varies with the change of the mass number of nuclei, which can be explained by the difference of their surface diffuseness. The relation of isotope-isotone effects to the diffuseness of a nucleus surface revealed while studying the dependence of the total cross-sections of reactions on the neutron excess is analyzed as well.