OBJECTIVES: Treatment persistence can be a good indicator of drug efficacy and tolerability.  Inhaled long-acting bronchodilators (e.g., long-acting β2-agonists [LABAs]) are the recommended maintenance treatment in moderate-to-severe chronic obstructive pulmonary disease (COPD).  Arformoterol and formoterol are the only two available nebulized LABAs. There is limited real-world head-to-head comparative evidence for nebulized LABAs. The objective is to evaluate the difference in their treatment persistence. METHODS: This retrospective cohort study of the PharMetrics Plus claims database included eligible (continuous health plan enrollment 180-day pre- and 360-day post-index) patients >35 years; with ≥2 prescriptions of nebulized LABAs between 2008-2011 (first use as index); COPD diagnosis (ICD-9-CM 491.x, 492.x, 496.x) with ≥2 outpatient or ≥1 inpatient claims. Patients were excluded if they received nebulized LABA treatment or asthma diagnosis in the pre-index period.  Persistence was defined as days from index to discontinuation (gap of ≥60 days) or end of study.  Chi-square and t-test were used to compare two cohorts (alpha=0.05).  Cox proportional hazards models were used to evaluate discontinuation risk 180- and 360-days post-index as a function of nebulized LABAs, age, physician specialty, comorbidities, initiation timing, and pre-index healthcare spending. RESULTS: A total of 1,041 eligible patients (arformoterol=672, formoterol=369) were included (mean age=69.4 years, 47.5% females). Compared to formoterol patients, arformoterol patients had longer treatment persistence (mean±SD: 210±133 vs. 192±137 days, p=0.0356), and lower predicted discontinuation risk (hazard ratio [HR]=0.78 [95% CI 0.65-0.93] in 180-day post-index and HR=0.87 [95% CI 0.75-1.00] in 360-day post-index models). Nebulized LABAs, non-pulmonologist prescribing, pre-index depression, and lower pre-index healthcare spending were associated with higher discontinuation risk in both 180- and 360-day Cox models. Younger age (35-54 vs. 65+ years) and pre-index diabetes additionally predicted higher discontinuation risk in 360-day Cox model. CONCLUSIONS: COPD patients on arformoterol had a higher treatment persistence compared to formoterol patients in this retrospective claims analysis.