Patients affected by Parkinson's disease are at a high risk for fractures, mainly of the hip. These fractures are caused by falls due to postural imbalance, neurological impairment and reduced bone mass. The purpose of this study was (1) to investigate the correlations and the pathophysiological mechanisms underlying bone loss in Parkinson's disease and appraise bone loss or fracture risk reduction interventions; (2) to develop a research agenda that informs the design and development of risk reduction strategies. Osteoporosis and osteopenia are very common findings in patients with Parkinson's disease, affecting up to 91% of women and 61% of men. Reduced bone mass in Parkinsonian patients seems to be caused mainly by reduced mobility through a mechanism similar to that observed in other neurological diseases. Endocrine (such as vitamin D deficiency), nutritional and iatrogenic factors also play an important role in bone mass depletion. Female gender, disease duration and severity (Hoehn and Yahr stages III and IV), old age and low body mass index are related to more severe osteoporosis. Vitamin D supplementation and bisphosphonates seem to be effective in reducing the risk of nonvertebral fractures in patients affected by Parkinson's disease. Prevention and evaluation of osteoporosis through bone mass density assessment should be considered in all patients with Parkinson's disease.