Comorbidities are frequent in chronic obstructive pulmonary disease (COPD) and significantly impact on patients' quality of life, exacerbation frequency, and survival. There is increasing evidence that certain diseases occur in greater frequency amongst patients with COPD than in the general population, and that these comorbidities significantly impact on patient outcomes. Although the mechanisms are yet to be defined, many comorbidities likely result from the chronic inflammatory state that is present in COPD. Common problems in the clinical management of COPD include recognizing new comorbidities, determining the impact of comorbidities on patient symptoms, the concurrent treatment of COPD and comorbidities, and accurate prognostication. The majority of comorbidities in COPD should be treated according to usual practice, and specific COPD management is infrequently altered by the presence of comorbidities. Unfortunately, comorbidities are often under-recognized and under-treated. This review focuses on the epidemiology of ten major comorbidities in patients with COPD. Further, we emphasize the clinical impact upon prognosis and management considerations. This review will highlight the importance of comorbidity identification and management in the practice of caring for patients with COPD.