BACKGROUND: Patients are asked to assume greater responsibility for care, including use of medications, during transitions from hospital to home. Unfortunately, medications dispensed via respiratory inhalers to patients with asthma or chronic obstructive pulmonary disease (COPD) can be difficult to use. OBJECTIVES: To examine rates of inhaler misuse and to determine if patients with asthma or COPD differed in their ability to learn how to use inhalers correctly. DESIGN: A cross-sectional and pre/post intervention study at two urban academic hospitals. PARTICIPANTS: Hospitalized patients with asthma or COPD. INTERVENTION: A subset of participants received instruction about the correct use of respiratory inhalers. MAIN MEASURES: Use of metered dose inhaler (MDI) and Diskus devices was assessed using checklists. Misuse and mastery of each device were defined as <75% and 100% of steps correct, respectively. Insufficient vision was defined as worse than 20/50 in both eyes. Less-than adequate health literacy was defined as a score of <23/36 on The Short Test of Functional Health Literacy in Adults (S-TOFHLA). KEY RESULTS: One-hundred participants were enrolled (COPD n = 40; asthma n = 60). Overall, misuse was common (86% MDI, 71% Diskus), and rates of inhaler misuse for participants with COPD versus asthma were similar. Participants with COPD versus asthma were twice as likely to have insufficient vision (43% vs. 20%, p = 0.02) and three-times as likely to have less-than- adequate health literacy (61% vs. 19%, p = 0.001). Participants with insufficient vision were more likely to misuse Diskus devices (95% vs. 61%, p = 0.004). All participants (100%) were able to achieve mastery for both MDI and Diskus devices. CONCLUSIONS: Inhaler misuse is common, but correctable in hospitalized patients with COPD or asthma. Hospitals should implement a program to assess and teach appropriate inhaler technique that can overcome barriers to patient self-management, including insufficient vision, during transitions from hospital to home.