The growing number of people suffering from chronic diseases such as cardiovascular diseases, respiratory disease, cancer, and diabetes, as well as their quality of life, is one of the challenges of the health system in the ۲۱st century. (۱) However, chronic patients with respiratory failure (CRF) are considered as one of the priorities of the World Health Organization (WHO) because it affects millions of people worldwide. (۲) It is the third leading cause of death, with an annual mortality rate of higher than ۹.۵ million people in the world. (۳) Accurate statistics on chronic respiratory insufficiency (CRI) in Iran are not available; however, the mortality rate due to this disease was equal to ۹.۸% of all deaths in ۲۰۱۹. (۴)۲CRI refers to a problem in the function of the respiratory system when it is unable to sustain arterial blood gases at an acceptable level. It is classified into two categories, i.e., hypoxemic, such as pulmonary fibrosis, and hypercapnic respiratory failure, including chronic obstructive pulmonary disease (COPD), neuromuscular disorders (NMD), and persistent asthma. (۵-۶) In all types of this disease, patients continuously experience disruptions in their daily physical and functional activities, problems in their mental and psychological conditions, such as fatigue, fear, anxiety, isolation, dependence on others, depression, and social problems due to the progressive nature and exacerbation of respiratory symptoms. (۷-۸) They always require long-term drug use and oxygen therapy to improve the signs and symptoms of the disease affecting their quality of life. (۹) This leads to exorbitant costs in pharmacological/non-pharmacological treatments, time expenditure, frequent hospitalizations, and many other problems in the family and community. (۱۰)WHO estimates that by ۲۰۵۰, the incidence of chronic diseases such as respiratory insufficiency and changes in the quality of life will increase with the growing population in Iran. (۱۱) Quality of life is defined as one’s perceptions of physical and mental status, level of independence, social relationship, interaction with the environment, and personal sets of beliefs and values. (۱۲) Correspondingly, health-related quality of life (HRQL), as part of the overall quality of life, comprises mental, emotional, social, and physical perceived well-being and reflects the subjective and objective evaluation of patients and how they respond to the disease. (۱۲-۱۳) Wilson and Cleary (۱۹۹۵) define it as being pleased and satisfied with one’s aspects of life, both affected by health and affecting the person's health. (۱۴)HRQL is one of the most multifaceted and essential concepts of clinical research on chronic diseases; researchers constantly investigate how to assess its various aspects with an appropriate instrument. (۱۵) Assessing this concept can improve clinical decision making, evaluating the quality of medical and nursing interventions, and monitoring the severity, progression, and prognosis of the disease. (۱۶) In addition, such instruments can lead to reliable results in measuring HRQL changes, effective treatment programs, predicting future outcomes, and policymaking in the health system of any society. (۱۶-۱۷) Furthermore, they can contribute to the care and treatment of the patients by having discriminatory, evaluative, and predictive properties. (۱۶) The most common instrument used to measure HRQL in patients with CRI has been the۳severe respiratory insufficiency questionnaire (SRI), developed by Wendish et al. in German in ۲۰۰۳. (۱۸) It was employed in several countries, including Finland (۱۹), England (۲۰), Portugal (۲۱), Japan (۲۲), Norway (۲۳), China (۲۴), and Spain (۲۵), due to the importance of cultural adaptation and validation in different research communities.Nevertheless, measuring HRQL has been neglected in research, education, and clinics in our country. Due to the importance of the growing incidence of respiratory insufficiency and HRQL, there is a need for local and specialized instruments, specifically adapted for the individual and social conditions of patients, facilities, existing treatment and care conditions, and culture. Therefore, the present study aimed to determine the psychometric properties of the HRQL questionnaire in chronic patients with SRI.