The present study was conducted in the Al-Najaf slaughterhouse, during the period from November 2020 to March 2021, were collected 200 specimens of infected liver and lungs of sheep and cattle. The objective of the study is to investigate the number of hydatid cyst infections in cattle and sheep to investigate the macroscopic and microscopic characteristics, number and size of cysts in each lung and liver, comparison between the thickness of cysts wall in the liver of sheep and cattle infested with echinococcosis. The results of the macroscopic study showed the total number of cysts found in the liver of slaughtered sheep was 673 in different size groups while in the lung of slaughtered sheep, the total number of cysts was 216 cysts in different size groups.  The examination of the lung of infected cattle during the period of our study revered no cystic lesions in the study while the total number of cysts found in the liver of slaughtered cattle was 158 in different group sizes, almost 50 % of the size of the hydatid cyst in the sheep liver is between 1-3 cm, while in cattle is between 3-5 cm. The microscopic investigation of the liver and lung specimens stained with hematoxylin and eosin stain and another stain was used in this study to evaluate the fibrous tissue proliferation via Masson's trichrome stain.  showed there were features of chronic inflammation in hepatic tissue of infested sheep and cattle by cystic echinococcosis represented by marginal fibrous tissue layer surrounding the hydatid cyst, infiltration of mononuclear cells, eosinophils, neutrophils, macrophages, and fibrocytes. The main conclusions of the study revealed that there were significant differences between the thickness of germinativum, laminated and adventitial layers of hydatid cysts in different size groups, and no hydatid cysts were recognized in the lung of slaughtered cattle during the study period.