The IRYSS-COPD appropriateness study was developed in 16 hospitals belonging to the Spanish National Health Service from June 2008 to September 2010 (n = 2,877). The objectives were to apply a set of explicit criteria for the appropriateness of hospital admission created by the RAND/UCLA methodology to patients evaluated in the emergency department (ED) for exacerbations of COPD. This is a prospective cohort study. We explored the relationship between appropriateness of admission as defined by the explicit criteria and the final decision to admit or discharge. A total of 2,877 patients were included for analysis; of these, 1,747 (60.7 %) were admitted and 1,130 (39.3 %) were discharged from the ED to home. Among patients classified by the explicit criteria as appropriate for hospital admission, 81.3 % were admitted, compared with 64.81 % of those classified as uncertain and 48.65 % of those classified as inappropriate for admission. Severity of exacerbation was the most influencing variable in the decision. Application of our explicit criteria for appropriate hospital admission among a large sample of patients experiencing an exacerbation of COPD in the ED setting suggests that these criteria could be used as the basis for clinical decision-making and health-care assessment.