The "obesity paradox" is defined as an inverse association of good health, survival and obesity. Usually in healthy persons the more obese you are the more metabolic complications you have; however, thin patients with chronic obstructive pulmonary disease (COPD) have more cardiovascular complications and a higher mortality rate. To explore whether atherosclerosis and peripheral artery disease (PAD) contribute to the higher morbidity and mortality of patients with COPD. This prospective study included 87 patients with chronic COPD who were treated in the pulmonary outpatient clinic; all signed a consent form before enrollment. We documented their lung function (FEV1%), body mass index (BMI) and ankle brachial index (ABI). The primary endpoints were to find an association between atherosclerosis and BMI in patients with COPD, and between atherosclerosis and severity of lung disease. Average ABI was 1.01 +/- 0.20, BMI was 29.33 +/- 7.48 kg/m2, and the abdominal circumference was 107.34 +/- 18.87 cm. A positive correlation was found between BMI and ABI (P=0.001) and between abdominal circumference and ABI (P=0.000). Patients with peripheral artery disease were older (73.6 +/- 11.5 vs. 68.1 +/- 11.6 years old, P= 0.04), were thinner (average BMI 25.5 +/- 6.2 vs. 31.06 +/- 7.3, P= 0.001), and had a lower abdominal circumference (97.7 +/- 18.3 vs. 111.7 +/- 17.5 cm, P=0.001). No such difference was observed for years of smoking. Male PAD patients with COPD had a lower BMI (25.2 +/- 5.6 vs. 29.9 +/- 7.4, P = 0.016), and their abdominal circumference was smaller (96.1 +/- 18.0 vs. 110.2 +/- 16.5 cm, P=0.004). Female PAD patients with COPD had a lower BMI (26.3 +/- 8.2 vs. 33.1 +/- 7.0, P=0.045), but their abdominal circumference was not different from females without PAD (102.0 +/- 19.7 vs. 114.0 +/- 19.4 cm, P=0.162). Patients with PAD had a worse lung disease (FEV1% 34 +/- 8% vs. 45 +/- 16%, P=0.01). During the 1 year of follow-up five patients died: two PAD patients due to acute myocardial infarction and three non-PAD patients died from pulmonary insufficiency (two patients) and pulmonary emboli (one patient). We found that COPD patients with PAD were older and thinner and had a lower abdominal circumference and a more progressive lung disease. Extensive atherosclerosis in patients with COPD may partly explain the "obesity paradox" observed in patients with COPD.