Spirometric detection of not fully reversible airflow limitation by forced expiratory volume in 1 s (FEV₁) is the integral result of a spectrum of different underlying pathological conditions called chronic obstructive pulmonary disease (COPD). Several observations of the past that have been confirmed in recent articles indicate that patients with COPD may have different clinical, functional, radiological, and pathological manifestations reflecting different pathophysiological mechanisms of expiratory airflow limitation. Computed tomography scanning provides in vivo information about the various pathological changes occurring in patients with COPD and permits differentiation of those with predominant airway obstruction from those with predominant emphysematous destruction. The development of a standardized method for classifying COPD phenotypes in clinical practice may have a great impact on understanding the results of pharmacological trials, clinical approach to patient treatment, and knowledge of the natural history of the disease.