Background and Objectives: During osteopetrosis course, impaired bone remodeling induces skeletal osteosclerosis and abnormally dense bones, which, however, are brittle and susceptible to low-energy fractures. In this study, radiological evaluation and densitometric measurements of several bones of the skeleton in one of the oldest patients in the world suffering from osteopetrosis was presented. Materials and Methods: Volumetric bone mineral density measurements of the examined bones in an 80-year-old man were performed using two different quantitative computed tomography techniques. Results: The obtained results show higher values of the volumetric bone mineral density of the trabecular bone in lumbar spine than in the cortical bone compartment. T-score and Z-score in this patient reached values of 27–28 and 31–32, respectively. Conclusions: The obtained densitometric data may serve for further diagnostic purposes of osteopetrosis. As documented, the severity of the osteosclerotic changes of bones were higher in this patient than in most other described cases. Moreover, radiological signs diagnosed in this patient were characteristic for all types of osteopetrosis making this case very uncommon.