While chronic obstructive pulmonary disease (COPD) is still characterized and diagnosed by lung function measurements, there is increasing evidence that the chronic diseases that frequently develop with COPD in response to the common risk factors (smoking, aging, obesity) may contribute significantly to its clinical manifestations and severity. Considering that pharmacologic and nonpharmacologic treatments of COPD, such as pulmonary rehabilitation, are primarily symptomatic, it is reasonable to hope that a more comprehensive management of COPD that takes into account its comorbidities may improve the response to treatment and reduce mortality in patients with COPD. Thus, as comorbidities are often underdiagnosed and undertreated, it is important to search for their coexistence in COPD and in all chronic diseases, possibly by adopting recommendations for diagnosis of single diseases. This means that while careful cardiovascular, metabolic, and endocrinologic examinations should be increasingly used in assessing patients with COPD, lung function measurements may become useful in patients with chronic cardiovalscular, metabolic, and endocrinologic diseases. The increasing evidence that active treatment of comorbidities (by, e.g., statins and beta-blockers) may reduce morbidity and mortality in patients with COPD suggests the urgent need for randomized clinical trials that hopefully will provide the evidence for more comprehensive clinical guidelines for these patients.