Cystic fibrosis related diabetes (CFRD) is a distinct form of diabetes that is associated with significantly increased morbidity and mortality in the CF population. The primary etiology is relative insulin insufficiency secondary to destruction of pancreatic islets, and to other factors that affect the function of the remaining beta cells. The prevalence of CFRD increases markedly with age and more than half of CF adults develop the disease. As the initial presentation of CFRD may be clinically silent, annual screening is recommended starting at least by the age of 10 with an oral glucose tolerance test (OGTT). The importance of an early diagnosis is based on the association of diabetes and abnormal glucose tolerance with worse health outcomes in patients with CF, and evidence that early treatment of diabetes improves prognosis. This review presents a concise overview of the current understanding of CFRD pathogenesis, natural history, screening and diagnosis.