The study aimed to develop a short, validated questionnaire to assess the impact of chronic obstructive pulmonary disease (COPD) on health status. The COPD Assessment Test (CAT) was created through a rigorous process involving qualitative research, international prospective studies, and psychometric analyses. The final CAT consists of eight items, each scored on a six-point scale, covering aspects such as cough, phlegm, chest tightness, breathlessness, activity limitation, confidence, sleep, and energy. The CAT demonstrated excellent internal consistency (Cronbach’s α=0.88) and good test-retest reliability (intra-class correlation coefficient 0.8). It showed strong correlation with the St George’s Respiratory Questionnaire (SGRQ-C) in the USA (r=0.80) and was sensitive to differences between stable and exacerbation patients (p<0.0001). The CAT is a reliable and valid tool for assessing and monitoring COPD, providing a standardized measure of health status with global relevance.The study aimed to develop a short, validated questionnaire to assess the impact of chronic obstructive pulmonary disease (COPD) on health status. The COPD Assessment Test (CAT) was created through a rigorous process involving qualitative research, international prospective studies, and psychometric analyses. The final CAT consists of eight items, each scored on a six-point scale, covering aspects such as cough, phlegm, chest tightness, breathlessness, activity limitation, confidence, sleep, and energy. The CAT demonstrated excellent internal consistency (Cronbach’s α=0.88) and good test-retest reliability (intra-class correlation coefficient 0.8). It showed strong correlation with the St George’s Respiratory Questionnaire (SGRQ-C) in the USA (r=0.80) and was sensitive to differences between stable and exacerbation patients (p<0.0001). The CAT is a reliable and valid tool for assessing and monitoring COPD, providing a standardized measure of health status with global relevance.