There have been few studies concerning osteoporosis in patients with Parkinson's disease (PD), even though patients with PD have a high incidence of falls. Using a Korean population, we investigated the association between bone mineral density (BMD) and PD. A total of 107 patients with PD were compared with age-matched and sex-matched normal controls. Using the Hoehn & Yahr staging system, we classified the patients with PD into three subgroups. Parts II and III of the Unified Parkinson's Disease Rating Scale were administered to evaluate the relationship between the severity of PD and BMD. In conclusion, in the PD population we found that decreased BMD was related to the severity of immobility of patients, and that BMD changes were greater at the femoral neck than the spine area. Therefore, we assert that clinicians should consider administering screening tests to elderly patients with PD and provide appropriate primary or secondary prophylactic treatment for osteoporosis.