We have studied the influence of gamma radiation on the structure of the photodiode and its current. Fifty-five photodiodes have been irradiated twice, the first dose of 2000 Gy and then a dose of 5000Gy. U-I characteristics of each photodiode have been measured several times, before the radiation, between the radiation and after radiation and presented on the same diagram. These diagrams show the influence of gamma radiation on photodiodes. The results show that gamma irradiation reduces the current of photodiode. After some time photodiodes have been recovered from the effects of radiation, but not completely. Some time after the second irradiation some unusual changes in photodiode current have been observed. Because of these two doses of radiation, the current of photodiodes have been reduced by 14-17 %.