A 17-year-old male patient with cystic fibrosis, advanced lung disease and finger clubbings presented symmetrical chronic arthritis of the knee and ankle joints of unknown origin. Hypertrophic osteoarthropathy diagnosed on the basis of the classic clinical features and anamnestic data was documented by the presence of periostosis of the tubular bones on radiographs. The considerably increased life expectancy of CF patients seems to mean the expansion of the list of diseases to be excluded when diagnosing JCA.