The traditional physiological definition of chronic obstructive pulmonary disease (COPD) is of practical use in encompassing the overlapping syndromes of COPD in routine clinical practice, and underpins the continued use of spirometry for diagnosis, screening, staging, and monitoring. However, the diagnostic criteria for COPD have not evolved in step with advances in understanding of pathogenesis, and this approach of including all the components of COPD under one umbrella is under question. The characterization of phenotypic variation is currently recognized to hold the key to better understanding of COPD pathogenesis and the identification of effective novel therapies. COPD demonstrates considerable heterogeneity, and, consequently, patient characterization requires a varied approach and the use of multiple modalities. This review discusses the methodologies that are currently used for patient phenotyping and the approaches that have been advocated for the identification of clinically meaningful phenotypes.