Neurofibromatosis-1 is a here-do-familiar disorder that is associated with a variety of skeletal anomalies, mostly with spinal deformities in 10-50% of the patients. Intraoperatively, a poor vertebral bone quality has been observed. Efforts have been made to identify factors preventing curve progression, to optimize operational planning and to explain the pathomechanism. As part of the preoperative evaluation, the authors used a dual X-ray absorptiometry to assess the bone mineral density of the lumbar spine in 12 non operated patients with neurofibromatosis-1, supplemented by laboratory blood/urine investigations. A significant decrease in bone mineral density of lumbar spine was measured. An inverse relation was suggested between the severity of scoliosis and the lumbar spine Z-scores. No pivotal alterations were identified in the laboratory measurements. The bony tissue abnormality observed intraoperatively in neurofibromatosis-1 patients may be described as a diminution of the axial bone mineral density. The evaluation of bone mineral density in the course of the preoperative planning is proposed in neurofibromatosis-1.