We investigated the prevalence of cystic fibrosis-related diabetes (CFRD) and its association with various demographic and clinical conditions in a Dutch child and adult cystic fibrosis (CF) population. Patients were classified as having either normal glucose tolerance (NGT), impaired glucose tolerance (IGT) or CFRD. Associations with the following parameters were studied: age, gender, BMI, mutations, pulmonary function, infection status, and hospitalization. In our patient population the prevalence of IGT and CFRD was 16% and 31% respectively. After excluding pancreatic sufficient patients, the prevalence of CFRD was 40% and in patients over 40 years 52%. Compared with patients with NGT, CFRD patients were older, had more in-hospital days and had worse pulmonary function. Women developed CFRD at a significantly younger age than men. CFRD is a frequently occurring co-morbidity in patients with CF. The prevalence of CFRD is increasing in ageing CF populations and deserves rising attention in CF management.