Improving quality of life (QoL) is an important goal in COPD disease management. There are many tools to assess the QoL of COPD patients, but the CAT questionnaire is considered valuable and reliable in practice. The study was conducted to determine the reliability and validity of the CAT questionnaire on COPD patients at Nghe An General Friendship Hospital. 150 stable COPD patients at a respiratory clinic were studied using cross - sectional description. The results showed that the average score of 8 research areas in stable COPD patients was 21.15. Clinical impact of COPD according to CAT score at moderate and high levels. COPD is common in men over 48 years old. Smoking, disease stage, difficulty breathing and FEV1 are all related to QoL. A strong, positive correlation between MRC and CAT has been found. The more severe the difficulty breathing, the worse the QoL - health. On the contrary, between FEV1 and CAT there is a negative, moderate correlation. The lower the FEV1 value compared to predicted value, the higher the patient’s QoL - health. There is a positive correlation between CAT and SGRQ. The total CAT score is high, the SGRQ score is also high. Therefore, CAT questionnaire can be widely applied in clinical practice to assess QoL - health in COPD patients.