INTRODUCTION: Osteoporosis is a common condition in patients with end-stage lung disease, but little attention has been given to bone disease in patients with primary pulmonary hypertension (PPH). The purposes of this study were as follows: (1) to determine the prevalence of osteoporosis in patients with severe PPH before lung transplantation, (2) to investigate whether generally accepted risk factors for osteoporosis would play a role in this special group of patients, and (3) to determine whether there is an association between functional parameters and pretransplantion bone mass. DESIGN: A retrospective analysis of 18 consecutive patients with PPH accepted for lung transplantation at the University Hospital of Zurich. MEASUREMENTS AND RESULTS: Decreased bone mineral density (BMD) [T score <- 1.0] was found in 11 of 18 patients (61%) at the femoral neck (FN) and 13 of 18 patients (72%) at the lumbar spine (LS). We did not find a significant difference of BMD in a gender- or age-specific manner. Body mass index (BMI) correlated significantly with BMD and T score at the FN and WT. Pulmonary vascular resistance (PVR) was notably linked with BMD at the FN. We found a positive association between walking distance in the 12-min walking test and BMD at the FN and WT. CONCLUSIONS: Low bone density is a very frequent condition in patients with severe PPH. In contrast to the general population, in our study group neither age nor female gender were significantly associated with lower bone mass. Body weight and BMI were highly coupled with BMD. Among the functional parameters, walking distance and PVR were correlated to BMD at the FN. Considering that patients with PPH may have an improved life expectancy in the future, the early diagnosis, prevention, and treatment of osteoporosis should receive high priority.