Disclosed is a use of aztreonam lysine in the manufacture of a medicament for improving the health-related quality-of-life score in a patient having cystic fibrosis, as measured by one, two, three, four, five, six, seven, eight, nine, ten, eleven or all of the 5 symptom domains of the Cystic Fibrosis Questionnaire-Revised, wherein said medicament is an inhalable dry powder or aerosol comprising about 1 to about 250mg of aztreonam lysine per one dose, and wherein the medicament is to be administered to the airways of the lung using a dosing regimen comprising administering said inhalable dry powder or aerosol 3 to 10 times a day for at least 28 consecutive days followed by a 28 day drug holiday and repeating the regimen two, three, four, five, six, seven, eight, nine or more times.
