Health-related quality of life (HRQOL) measurements provide valuable information about the psychological and social impact of treatment on patients with cystic fibrosis (CF). This study evaluated the HRQOL of Brazilian patients with CF and assessed the changes in HRQOL domains over 1 year after dornase alfa (Pulmozyme) introduction.One hundred fifty-six stable patients with CF and 89 caregivers answered the Portuguese-validated version of the Cystic Fibrosis Questionnaire-Revised (CFQ-R) at baseline (T(0)), and at 3 (T(1)), 6 (T(2)), 9 (T(3)), and 12 (T(4)) months of follow-up. Eighteen patients were excluded because they did not fulfill the inclusion criteria. The patients were analyzed in two groups: those aged 6-11 years and those aged 14 years and older. ANOVA for observed repeated results and the last observation carried forward (LOCF) method for missing data were used for the statistical analysis.