Aim: Study of knowledge and practice of dry powder inhalation among patients with chronic obstructive pulmonary disease in Bihar region. Methods: A cross-sectional study was conducted in the Department of Medicine, Darbhanga Medical College and Hospital, Laheriasarai, Darbhanga, Bihar, India for 1 year. Total 100 patients diagnosed COPD, who had been using a rota haler since the last 1 month was identified using the examination card and the laboratory and radiological findings of the patients. The questionnaire was administered by the interviewer in a separate room in the OPD (between the OPD time of 9 am and 2 pm). Regarding knowledge, the frequency of correct answer on each question was given the score of 1. Then, assessment of the dry powder inhalation technique was conducted using the rota haler with placebo rota caps in the same room. Results: The overall mean and SD of the age of those users was 68.22 8.92. Regarding instruction, nearly all (99%) of the rota haler users got verbal instruction regarding the use of the rota haler. However, only 13% of the respondents had observed a demonstration of dry powder inhalation from health care providers. The majority of the DPI users (89%) had correct knowledge about the storage of rota caps. They were aware that rota caps should be kept in a cool place away from moisture, and four- fifths of them (80%) were aware that they should take a slow deep breath while inhaling the drug. However, only 12% of them possessed the correct knowledge on holding breath for 10 seconds after deep inhalation of the drug. Regarding practice, the item most correctly performed by the rota haler users was keeping the Rotacap horizontal (99%) followed by keeping the rota haler upright (99%) and opening the rota haler and discarding the empty capsule (97%). In respect to all the steps of the dry powder inhalation, a minority (4%) of the patients demonstrated the use of the rota haler correctly, while most of them (96%) performed the steps incorrectly. There is statistically significant association of practice of dry powder inhalation with a demonstration of dry powder inhalation by health care providers (p=0.001). Conclusion: It is concluded that COPD patients using the Rota haler and attending our Hospital possessed a satisfactory level of knowledge and poor practice of dry powder inhalation. Regarding practice, the most commonly performed error among Rota haler users is not exhaling prior to inhalation followed by the inability to hold one’s breath for 10 seconds.