The aim was to determine and evaluate the morphological picture of the lungs of experimental animals under the influence of chronic irradiation. It was found that the macroscopic picture of the lungs of white outbred rats of the main and control groups were unchanged. The study of the microscopic picture of the lungs revealed no pathomorphological changes in the control group. In laboratory animals that received chronic irradiation, pathomorphological signs were found, in the form of plethora of the segmental vein, venous plethora in the peribronchial vessels, dystrophic changes in the interstitial tissue of the lungs, and growth of the wall of small bronchi due to fibrosis, thinning of the alveolar wall, changes in the bronchial wall and formation of connective tissue were noted. tissue, lymphocytic infiltration between the bronchi and interstitial tissue, focal emphysema. It has been proven that these pathomorphological changes were the result of the negative effect of chronic irradiation on the lungs of white outbred rats.