Inhalation therapy plays a crucial role in the treatment of bronchial asthma and chronic obstructive pulmonary disease. It is therefore important to choose the best inhaler device for individual patients and to provide precise instructions on its usage. This study assessed an eight-step instruction process for inhalation therapy (preparation of the drug, expiration before inhalation, inhalation, breath-holding after inhalation, expiration after breath-holding, cleaning up, gargling after inhalation, and checking the amount remaining) in the outpatient department of Kobe City Medical Center West Hospital. A total of 214 patients were instructed over the course of one year with good results. However, in patients aged ≥75 years, significantly more cases of insufficient understanding were observed for the steps of inhalation (p<0.001), breath-holding after inhalation (p=0.028), gargling after inhalation (p=0.019), and checking the amount remaining (p=0.015). Moreover, in patients using a pressurized metered-dose inhaler, half of the cases required re-instruction. Patients receiving inhalation therapy, especially elderly patients, should be instructed in the inhalation technique as well as in breath-holding and gargling after inhalation.