OBJECTIVES: COPD is a chronic lung disease that has a detrimental effect upon patient’s quality of life. The COPD Assessment Tool (CAT) has been developed to measure the impact of the disease. This research explores the relationship between the disease-specific CAT, and the general health related utility measure EQ-5D. METHODS: COPD is a chronic lung disease that has a detrimental effect upon patient’s quality of life. The COPD Assessment Tool (CAT) has been developed to measure the impact of the disease. This research explores the relationship between the disease-specific CAT, and the general health related utility measure EQ-5D. RESULTS: A scatter plot relating CAT score to EQ-5D showed that the relationship is non-linear.  Variance of the EQ-5D score increased with CAT score, suggesting the increasing influence of confounding factors for patients reporting a higher CAT score (CAT score range variance: 0-10: 0.013, 11-20: 0.026, 21-30: 0.050 and 31-40: 0.126). A generalized linear model was used to account for the non-linear relationship, and control for confounding influences of age, gender, physician-perceived COPD severity and number of concomitant conditions, with no assumption of constant variance. The relationship between CAT and reversed EQ-5D was positive and significant (coefficient 0.070, p-value <0.0001), illustrating higher CAT score was associated with lower EQ-5D.  A one point increase in CAT score resulted in an approximate 7.2% relative decrease in EQ-5D score.  Similarly, significant (p-value <0.0001) negative relationships observed for older patients (coefficient 0.016), female gender (coefficient 0.147), greater severity (coefficient 0.469), and a higher number of comorbidities (coefficient 0.070). CONCLUSIONS: Increasing COPD impact as measured by the CAT was associated with lower EQ-5D scores. However, the increasing variance of EQ-5D for patients with higher CAT scores demonstrates the need for both COPD impact and overall health status assessment.