Background: Chronic Obstructive Pulmonary Disease (COPD) is a common lung disease that interferes with basic functions of elderly breathing. Aim: to assess the respiratory functions among the elderly with COPD on the irk now ledge and practice. Subjects and methods: Descriptive cross sectional research design was used to conduct this study in Chest Departments at the Main Assuit University Hospital. Purposive sample of 169COPD elderly was participated. Three tools were used includes: 1st tool: Elderly assessment sheet, it includes two parts (Socio-demographic& health history and Bristol COPD knowledge assessment sheet), 2nd tool: Observational checklists used to assess the practice of elderly: (breathing & coughing exercise, inhaler technique) and 3rd tool: Respiratory functions assessment sheet used to evaluate the (dyspnea grade, oxygen saturation, respiratory rate and peak flow meter). Results: The main age of studied sample 65.50±5.16 (60-78), 73.4% were male and 70.4% were smokers. The vast majority of studied sample had poor knowledge & practice with impaired in respiratory functions. Conclusion: Vast majority of the studied elderly had poor knowledge & practice which had negative impact on respiratory functions. Recommendations: Health education program for elderly with COPD to improve their knowledge & practice and respiratory functions is very essential to manage their disease.