BACKGROUND: The fixed-dose combination of budesonide/formoterol (B/F) has been available in the Spiromax® dry powder inhaler since 2014. OBJECTIVES: To assess patient satisfaction, inhaler use errors, and disease control in patients with asthma or chronic obstructive pulmonary disease (COPD) treated with B/F Spiromax. METHODS: This non-interventional, prospective, 12-week study enrolled consecutive asthma or COPD patients who had recently begun treatment with B/F Spiromax or were switched from another inhaled corticosteroid/long-acting β2-agonist combination to B/F Spiromax in routine clinical practice. Patients recruited from 243 specialist respiratory clinics or general practices in Germany were assessed for patient satisfaction (Satisfaction with Inhalers and Preference questionnaire), inhaler application errors (modified Easy Low Instruction over Time checklist), disease control, and safety. RESULTS: The population included 3,943 patients: asthma n = 2,707 (68.7%); COPD n = 1,236 (31.3%). At baseline, 60.1% of patients were "satisfied" or "very satisfied" with their previous inhaler, and this increased to 88.8% at week 12 of B/F Spiromax use. Overall, 62.1% of pre-treated patients preferred B/F Spiromax to their old inhaler. The frequency of any handling error observed with B/F Spiromax at week 12 was lower than at baseline (11.9 vs. 25.5% of patients, respectively). After 12 weeks, 77.4% were assessed as having improved (minimally, much, or very much) overall health status versus baseline. Guideline-defined disease severity (as rated by physicians) and patient-reported symptom severity improved during the study in both asthma and COPD patients. B/F Spiromax was well tolerated. CONCLUSION: B/F Spiromax was associated with high patient satisfaction, low device handling error rate, and improvements in clinical outcomes in real-world clinical practice.