OBJECTIVES: Patient-reported symptoms of chronic obstructive pulmonary disease (COPD) provide important supporting information about how patients feel and function in addition to objective measures of pulmonary function. This analysis characterized the symptom response profiles of patients with moderate to severe COPD who initiated treatment with arformoterol or placebo. METHODS: Data for this post-hoc analysis came from a large, randomized, double-blind, safety trial of nebulized arformoterol 15µg BID (n=420) or matched placebo (n=421). Treatment with other non-long-acting beta agonists was permitted. This post-hoc analysis examined changes in the symptoms subscale of the St. George’s Respiratory Questionnaire (SGRQ). Growth Mixture Modeling (GMM) examined variability in individual responses over the 12-month study period and identified latent classes of differential responders conditional on treatment. Follow-up analyses characterized the baseline and treatment outcome profiles for the different latent classes. RESULTS: The symptom score response profiles were best explained by two latent classes that were labeled “responders” and “non-responders.” Relative to “non-responders” (n=259), “responders” (n=571) were lower in age (63.0 vs. 65.1), more likely to smoke (55.5% vs. 44.0%), had more severe baseline symptoms score (75.4 vs. 46.0), and lower forced expiratory volume (liters) in one second (FEV; 1.16 vs. 1.23). Responders had significantly greater improvements in symptoms (-8.8 vs. -1.6), but not in FEV (0.05 vs. 0.03). Among the responders, those treated with arformoterol had comparable improvements in symptoms (-10.3 vs. -7.2, p>0.05) and a similar number of exacerbations (0.55 vs. 0.69, p>0.05), but significantly greater improvements in FEV(0.09 vs. 0.008, p=0.03) and significantly fewer hospitalizations (0.13 vs. 0.24, p=0.02). CONCLUSIONS: In this analysis, symptom response profiles were best explained by two latent classes. Among the responders, arformoterol appeared to improved lung function and reduce hospitalizations. Arformoterol may be particularly effective among patients who are unable to quit smoking and have more severe symptoms.