The actual burden of chronic obstructive pulmonary disease (COPD) in terms of health care use and costs strongly depends on the distribution of disease severity. For the Netherlands, the distribution of diagnosed COPD was estimated by classifying all patients with a physician diagnosis of COPD from two different sources of general practitioners (GP)-data into mild (27%), moderate (55%), severe (15%) or very severe COPD (3%) based on their post-bronchodilator FEV1% predicted, according to the GOLD-guidelines. This distribution will most likely shift to the less severe stages when under-reporting and under-diagnosis are reduced.