Chronic Obstructive Disease (COPD) is a disorder of respiratory system characterized by progressive and not-completely reversible airflow obstruction. Although the term obstruction is in the acronym, most international documents refer to it as airflow limitation (FL). Infact FL is a pathophysiologic condition in which the progressive increase in transpulmonary pressure is not associated with any change in airflow. FL is the king mechanism of dynamic hyperinflation which is the cause of symptoms for most patients. Some studies have documented that bronchial obstruction and airflow limitation are not synonyms. The aim of this work was to assess the relationship between FL, the severity of airflow obstruction, air trapping, and static hyperinflation in a group of COPD patients with different degrees of FEV1 reduction. The results show that the presence of airflow limitation cannot be predicted by any of the examined pathophysiologic variables. Therefore the assessment of FL should be an integral part of the general examination of COPD patients in the clinical practice.