The high prevalence and chronicity of chronic obstructive pulmonary disease (COPD) imply that many of these patients are treated and controlled in primary-care centres, often without contact with specialized pneumologist care. We conducted the present study to evaluate the treatment administered in stable and exacerbated COPD in GP-setting clinics and to investigate which factors could be associated with the different prescriptions. This is a cross-sectional observational study of ambulatory COPD patients. General practitioners (n = 201) were selected throughout Spain by regionally stratified sampling. We recorded the physician-reported prescription drug use in ambulatory treatment of stable COPD and acute exacerbations of COPD through a standard questionnaire. Factors independently associated with the prescription of drugs were ascertained by multiple logistic regression analysis. Of 1078 questionnaires reviewed, 1001 fulfilled quality criteria. There were 878 men (88%) and 123 women (12%); 777 (78%) were smokers or ex-smokers with a mean age of 68 years. Mean FEV1 was 47% predicted (% pred.) (SD = 13%). The median number of exacerbations was two per year (range = 0-16). Regular treatment for COPD was received by 878 (88%): the most commonly used drugs were inhaled beta 2-agonists (71%), theophyllines (53%) and inhaled corticosteroids (ICs) (50%), followed by mucolytics (25%), ipratropium bromide (23%), and oral corticosteroids (OCs) (4%). Treatment for exacerbations included inhaled bronchodilators (90%), antibiotics (89%), ICs (71%) and OCs (43%). Impairment of FEV1 was the factor most strongly associated in multiple regression analysis with increasing drug prescription in stable COPD, except for mucolytics, while the number of previous acute exacerbations was the main factor associated with exacerbation treatment except for OCs, the use of which was associated with more impaired pulmonary function. A significant number of the treatments prescribed in primary care for stable and exacerbated COPD do not follow current recommendations. Impairment in FEV1 is the factor most strongly associated with increasing prescription in stable COPD and the number of previous exacerbations is the main factor associated with exacerbation treatment.