Cystic fibrosis (CF) is the most common autosomal recessive disorder among Caucasians that significantly shortens life expectancy. In recent decades we have gained an abundance of new insights and better understand the pathophysiology of the disease. This enabled improved diagnostic and therapeutic approaches, but also revealed the complexity of the disease. CF is a progressive disease that is treated from the moment of diagnosis to the end of a person’s life, and over time, patients develop different and overall more complex clinical presentations. The consequence of gene mutation in CF is the dysfunction of a protein – cystic fibrosis transmembrane conductance regulator (CFTR), a protein that acts as a chloride channel and is expressed on epithelial cells in the exocrine glands and elsewhere in the body. Although the most severe symptoms of CF are related to the lungs, the disease affects multiple organ systems, and nearly half of all CF patients develop a type of diabetes called cystic fibrosis related diabetes (CFRD). It is a distinct form of diabetes, a direct consequence of CF, and shares some of its characteristics with both type 1 and type 2 diabetes. This thesis reviews the current understanding of CFRD pathogenesis, describes clinical presentation, screening and diagnostic methods as well as modern treatment methods. The primary cause of CFRD is relative insulin insufficiency caused by the destruction of the pancreatic islets of Langerhans. The initial phase of the disease is often asymptomatic, thus active screening for the disease in CF patients is recommended from the age of ten onwards, performing oral glucose tolerance test once a year. As CFRD increases morbidity and mortality in CF patients, early recognition and therapy initiation are important to prevent adverse clinical outcomes. CFRD therapy involves monitoring blood glucose levels and keeping those levels within normal limits. This is most often achieved with insulin and an appropriate diet that is significantly different from the diet for other types of diabetes.