OBJECTIVE: To determine whether previously reported socioeconomic status (SES)-related disparities in cystic fibrosis (CF) health outcomes vary by the indicator used (median household income by zip code [MIZ], maternal educational attainment [MEA], and state insurance coverage [MA]), and whether these disparities can be explained by differences in medical treatment. STUDY DESIGN: A cross-sectional analysis of data on patients age <18 years from the Epidemiologic Study of Cystic Fibrosis (ESCF). RESULTS: Disease severity showed a similar inverse correlation with all 3 SES measures. The number of stable clinic visits was unrelated to SES. Patients with MA had more sick outpatient visits and more courses of intravenous (IV) antibiotics for pulmonary exacerbations, and were more likely to be prescribed all chronic therapies. Low-MIZ patients had slightly fewer sick visits and more courses of IV antibiotics, and were more likely to receive oral nutrition supplements but less likely to receive macrolide prescriptions. Low-MEA patients were less likely to receive IV antibiotics at home, more likely to receive oral nutrition supplements, but less likely to receive macrolide prescriptions. CONCLUSIONS: CF health outcomes are correlated with the SES spectrum, but these disparities are not explained by differential use of health services or prescription of chronic therapy. Future investigations should focus on the possible impact of environmental exposures and differences in disease self-management.