Chronic obstructive pulmonary disease (COPD) is a leading cause of morbidity and mortality. A major goal of treatment is to ensure optimization of the level of health of the patient, i.e., health status as good as possible for the individual level of disease severity. For a number of reasons, patients with COPD tend to understate the overall severity of their condition, and the ways in which it impacts on their life. This underestimation and/or understatement of the impact of COPD can contribute to sub-optimal management of COPD, by making it difficult for healthcare professionals to assess the full impact of the condition on their patients’ lives accurately and to assign treatment appropriately. There is a need for a tool that is short and simple, self-administered by the patients, suitable for routine use in clinical practice and a reliable and valid measure of the impact of COPD on the life and health status of the patient. It should ensure that patients and healthcare professionals have a common understanding of the impact of the illness, and that their priorities with regard to management are in agreement. When used in conjunction with measurements of lung function, the tool should enable healthcare professionals to optimize the management of each individual patient. The COPD Assessment Test (CAT) was developed to facilitate a meaningful discussion between healthcare professionals and patients and provide a reliable measure of the impact of COPD on the patient’s life. Αs a result of this enhanced communication, the CAT is expected to contribute to improvements in the management of COPD and in the quality of life of the patients. The development and assessment of CAT was supported by the pharmaceutical company GlaxoSmithΚline.