The main objective is to evaluate HbA1c levels in patients with cystic fibrosis-related diabetes (CFRD) after one-year of therapy with elexacaftor/tezacaftor/ivacaftor (ETI). The secondary objective is to study the changes in total daily insulin dose (TDD), pulmonary function and metabolism in this population. A retrospective sin gle-center observational study was conducted at Regional Cystic Fibrosis Centre and Diabetology Centre of IRCCS Istituto Giannina Gaslini. The observation period was divided into Time 0 (ETI treatment initiation), Time 1 (T1 – 3 months of ETI therapy), Time 2 (T2 - 6 months of therapy) and Time 3 (T3 - 12 months of therapy). Demographic and clinical data were collected. The results were then stratified by genotype (F508del in homozygosity or heterozygosity). Twenty-eight patients with CFRD undergoing insulin therapy were included. TDD (IU) significantly decreased at T1 and T2, but not at T3, as for HbA1c. The number of hospitalizations and pulmonary exacerbations decreased significantly. We demonstrated both improvement in glycemic control (by means of HbA1c) and insulin requirement in insulin dependent CFRD patients after one year of only ETI treatment.