Comorbidities are important events in the natural history of the illness and have a negative impact on the morbidity and mortality of COPD patients. Although airflow limitation is the main clinical problem, patients within the same stage have widely varying symptoms and mortality risks. The body constitution plays a significant role in the heterogeneity of COPD. In this chapter, we have focused on cachexia and obesity that affect the body structure in patients with COPD.