Aim: In this study, we aimed to compare DEXA and CT densitometry in the diagnosis of osteoporosis and to evaluate the contribution of Hounsfield Unit calculation to the diagnosis of osteoporosis. Also, we examined the bone mineral loss in osteoporosis by CT volumetry on lumbar vertebrae and femur neck. Materials and Methods: A total of 102 patients (51 females, 51 males) who underwent DEXA and CT densitometry on the same day were evaluated according to their measurements of lumbar vertebrae and femur neck. The DEXA T-scores and BMD values of L1-L2-L3-L4 vertebra bodies and femur neck were compared with CT densitometry HU values which were measured as the same regions. Also, CT volumetric measurements of vertebral bodies and femur neck were compared with DEXA results of the same regions. Results: A statistically significant correlation between DEXA results and CT HU values of lumbar vertebrae and femur neck was found as DEXA T-score and BMD value increase, CT HU value increased. CT HU values of patients which were classified according to WHO classification (osteoporosis, osteopenia, and normal density groups) were found to be statistically significantly different. We observed that an L1 vertebra corpus HU value < 161 and a femur neck HU value <96 suggest an increased risk of osteoporosis. As age increases, CT HU value statistically decreased. Also, we detected that DEXA T-score and BMD values of lumbar vertebrae and femur neck were correlated with CT volumetric measurements of these regions. Discussion: CT densitometry of lumbar vertebrae and femur neck may be an alternative method to DEXA for the diagnosis of osteoporosis. We suggest that a CT densitometry technique with a low-dose scan of an ideal region may be a promising modality for the diagnosis of osteoporosis.