37 patients with CF were recruited, 11 of whom were under modulators treatment. Blood samples were taken every 3 months for 21 months and at the beginning and at the end of any respiratory exacerbation. The microvesicles (MV) were counted and their number was proportional to the worsening of the patient’s pulmonary condition and in correlation with the beginning and resolution of the respiratory relapses. Conversely, the number of MV was lower in patients under treatment with modulators in respect of not treated; moreover the higher the number of MV the more serious the respiratory picture. These results need confirmation by increasing the number of subjects, but in any case, the MV count may be of clinical relevance. It will also be necessary the evaluation of the role and the function of MV in the development and evolution of CF pulmonary disease.