This is a prospective, observational study involving three Cystic Fibrosis (CF) adult patients, evaluating the changes in chest magnetic resonance imaging (MRI) three months after the start of elexacaftor/tezacaftor and ivacaftor therapy. MRI showed a drastic reduction in mucus plugging and bronchial wall thickening, with an improvement in the diffusion-weighted MRI score. Similarly, a marked improvement in spirometric parameters, nutritional status, and sweat chloride was observed. Our preliminary data confirm that chest MRI could be a useful tool to assess disease progression in CF patients on modulatory drug therapy.