The purpose of this study was to assess bone mineral density in a cystic fibrosis (CF) outpatient clinic population and to investigate the relationship between BMD and forced expiratory volume in one second (FEV1), DEXA T-scores and 25-hidroxivitamin D (25-OHD) serum levels. We examined a consecutive series of 44 CF patients. Bone mass density was measured by dual-photon X-ray absorptiometry of lumbar spine and femur (total and neck) and lung function was performed in all patients. Medication data were obtained from medical records. A correlation analysis was performed to determine the relationship between BMD and forced expiratory volume in one second (FEV1), DEXA T-scores and 25-hidroxivitamin D (25-OHD) serum levels. In the results, age showed a significant inverse correlation indicating that as the age increases, bone density decreases and we concluded that most CF patients have low BMD and that there is a positive correlation with lung function and an inverse correlation with age.