Abstract: Inonising irradiations used mostly in the treatment of tumoral deseasses are: X γ, β and e iradiations. The aim of this study is the investigation of gradient of β-particles irradiation energy. The discussion will be about radiations, produced in linear accelerators, electron energy from 5-14 MeV. It is important to know, the absorption performance, before and after, the electronic equilibrium. Weve use the function of dose gradient for iradiations β. It represents the velocity of dose change as a function of depth in tissue. From skin to maximum dose value, the increase of G-function is more accentuated for γ-rays than for β-particles while after that the G-function decreasing is less sharp for γ-rays while for β-particles it is almost promptly. This fact, allow us to use in radiotherapy not only γ-rays but β-particles too. The lasts, represents, a much more efficient tool, especially in terms of radiation protection of health adjacent tissues and organs. Finally we’ll discus, about the advantages in terms of radiation protection of β-particles used in radio therapy.