One of the extrapulmonary effects of chronic obstructive pulmonary disease (COPD) is osteoporosis. Osteoporosis is characterized by a low bone mineral density (BMD) and microarchitectural deterioration. Most studies in COPD patients use dual energy absorptiometry (DXA) scan only to determine osteoporosis, therefore microarchitectural changes without a low BMD are missed.Aim of the current study was to determine the prevalence and correlates of osteoporosis in COPD patients based on DXA-scan, X-ray of the spine (X-spine) and the combination thereof.DXA-scan, X-spine, pulmonary function testing, body composition, 6-minutes walking distance, medical history and medication use were assessed in 255 clinically stable COPD outpatients of a large teaching hospital in the Netherlands.Half of all patients had radiological evidence for osteoporosis. Combining the results of DXA-scans with X-spine augmented the proportion of COPD patients with osteoporosis compared to both methods separately. The prevalence of osteoporosis was not significantly different after stratification for GOLD-stage. Most patients with osteoporosis did not receive pharmacological treatment. Age, body mass index (BMI) and parathormone (PTH) were significant independent correlates for osteoporosis.Chest physicians should be aware of the high prevalence of osteoporosis in COPD even in case of a low GOLD score. Especially in elder COPD patients with a low BMI and/or an increased PTH. (c) 2010 American Society for Bone and Mineral Research.