Aim: To evaluate the response rate to antimycobacterial drug therapy in patients with cystic fibrosis (CF) suffering from infection by non-tuberculous mycobacteria (NTM). Methods: Ten patients, aged 10–34 y, out of 180 CF patients, were diagnosed with NTM disease. They had been regularly checked and examined for pulmonary symptoms, and had had chest X-rays and sputum cultures (including for mycobacteria) performed. One additional 36-y-old female received her CF diagnosis soon after the NTM diagnosis. Results: Mycobacterium avium-intracellulare complex (MAC) was found in 10 out of 11 patients and M. kansasii in 1 patient. Treatment with antimycobacterial drugs resulted in clinical improvement (weight gain or stabilization of weight and/or improved or stabilized lung function in 8 out of 11 patients) and mycobacterial culture turned negative in 10 out of 11. Conclusion: Promising results may be associated with early intervention with antimycobacterial therapy in CF patients.