OBJECTIVES: To determine if the average cost of medical care among cystic fibrosis (CF) patients with Pseudomonas aeruginosa (PA) infection is different across age-groups.  METHODS: Data were derived from MarketScan claims database, which captures person-specific direct medical utilization, expenditures, and enrollment from approximately 150 payers.  A retrospective cross-sectional study design was used.  CF subjects with an initial claim for a PA infection were identified using international classification of diseases diagnosis codes of 277.0 and 482.1, respectively. Demographic information from administrative claims and health care utilization and costs from medical and pharmacy claims were extracted for 12 months pre and post initial PA claim.  All resource use and costs were annualized and compared across 7 age-groups with parametric (ANOVA) and Duncan’s post-hoc tests using SAS version 9.2.  RESULTS: A total of 347 CF subjects with PA infection met the study criteria with mean age 19.9 (SD: 15.4) years and 47.8% females.  A monotonic trend of increasing (p<0.05) overall post period costs was observed across the 7 age-groups.  Example, children 0-4 years had the lowest (p<0.05) overall post costs of $31,569 (median=$22,887) vs. $95,024 (median=$36,783) for adults 45-64 years.  A similar trend with the exception of age group 30-44, was observed with PA-related costs as well. Mean and median per patient per year PA-related costs were lowest in children 0-4 years ($12,472, $3,572) compared to the oldest age-group of 45-64 years ($26,673, $3,311). In general, total prescription claims and outpatient visits, and PA-related inpatient visits increased with increasing age groups. Among children, PA-related prescription claims were statistically higher.  For example, mean PA-related prescription claims were 1.4 vs. 3.8 in the 0-4 vs. 15-19 groups (p<0.05).  CONCLUSIONS:  Overall and PA-related healthcare resource use and costs tended to vary across age groups.  Future research needs to explore the underlying reasons for this trend.