Background: Pharmacological treatment of chronic obstructive pulmonary disease (COPD) is mainly based on inhaled medications. Inappropriate use of inhalers due to the unrecovered peak inhalation ow rate (PIFR) results in an increased risk of early treatment failure. Therefore, this study was carried out to address the error patterns in using dry powder inhalers (DPI) versus pressurized metered-dose inhalers (MDI) inhaler devices among COPD patients with acute exacerbation. For this Methods: prospective cohort study, a cohort of 138 COPD patients with acute exacerbation were included from a tertiary care hospital in Karnataka. The inhalation technique and PIFR were evaluated at discharge and twice in follow-up at 15-day and 90 days intervals based on a list of the most common errors in the inhalation techniques. About 63% Results: of patients had comorbidities. The average length of hospital stay was 7.8 days and the mean PIFR value at discharge was 58.9L/min. About 51.4% of the COPD patients were MDI users and 48.6% were DPI users. The most frequent errors were inappropriate inhaling and short breath holding time for DPI (89.6% and 88.1%) and MDI (84.5% and 94.3%) device users, respectively. At follow-ups, these errors- inhaling deeply and shortbreath holding time continued to occur signicantly during 90-day follow-ups for DPI (79.1% and 82.1%) and MDI (79.2% and 90.1%) device users, respectively. However, the breath-out and mouthpiece placing errors were reduced signicantly at 90 days of follow-up among the DPI (50.7% and 40.3%, respectively) and MDI users (47.9% and 19.8%, respectively). Inappropriate inhali Conclusions: ng and short breath holding time were the most frequent and major errors made by inhaler device users. This emphasizes the training in proper inhalation techniques for COPD patients treated with inhalers