Low bone mineral density (osteoporosis) is prevalent in adults with cystic fibrosis (CF); they have an increased rate of bone fractures in comparison to the general population. CF patients start to lose bone density in adolescence/early adulthood due to an imbalance in bone breakdown and formation. Predicted survival for patients with CF has increased from 16 years in 1970 to 36.5 years in 2009 which has resulted in an increase in comorbidities associated with increased longevity in CF e.g. decreased bone density. Oral and intravenous bisphophosphonates are known to increase bone density in CF; the current licensed oral preparations require daily or weekly dosing which are difficult to maintain. Zoledronate, which is licensed for use, is administered intravenously once a year which should be easier to administer. The current evidence relates to its use in other disease groups e.g. glucocorticoid induced osteoporosis and oncology. The purpose of this study is to ascertain its efficacy in cystic fibrosis.