Comorbidities of chronic obstructive pulmonary disease (COPD) include pneumonia, pulmonary embolism, lung cancer, musculoskeletal dysfunction, osteoporosis, gastroesophageal reflux disease, cardiac disease, diabetes, hyperlipidemia, anemia, and sleep dysfunction, amongst others. These medical conditions are commonly reported in COPD patients; however, the true prevalence of these conditions based on epidemiological studies is variable. Tobacco exposure is a common risk factor between COPD and many of its comorbidities but there is recent evidence that suggests that the harmful effects of these conditions on COPD is independent of their association with smoking. There has recently been an increasing focus on the impact that these health problems may have on the morbidity and mortality associated with COPD as these are now being recognized as part of the overall burden of the disease. It remains to be seen whether or not effective treatment of COPD reduces the risk of developing one of the comorbidities associated with it as well as if interventions that address specific comorbidities, such as improving anemia or preventing, will alter the natural course of COPD. Further investigation is required to gain a better understanding of the interrelationship between COPD and its comorbidities.