The contribution of Ionizing Radiation (IoR) in diagnosis and therapy increases every day. Therefore it is considered one of the most popular genotoxic exogenous agent. Hence the estimation of DNA damages due to the applied IoR dose is a must. There are many techniques used for the detection of DNA damage that depend on different measurable parameters. In this work, Comet and Cytochalasin-B Blocked Micronucleus (CBMN) assays were applied in order to detect the extent of DNA damage due to the exposure to different doses of gamma rays. Peripheral blood lymphocytes were exposed to doses of 2, 4, 6, and 8 Gy from ¹³⁷Cs gamma-radiation source. Measured Comet assay dose parameters (tail DNA, tail length and tail moment) exhibit a significantly high correlation (p < 0.01) with the exposure dose. However, micronuclei (MNi) (CBMN parameter) showed a p-value greater than 0.05. Thus we can conclude that Comet assay is evidently more reliable than CBMN in the estimation of the magnitude of DNA damage in peripheral blood lymphocytes due to exposure to gamma radiation.