Ghrelin, a novel growth hormone-releasing peptide, has been shown to cause a positive energy balance by reducing fat use and stimulating food intake. This study investigated whether plasma ghrelin is associated with clinical parameters in patients with chronic obstructive pulmonary disease. Plasma ghrelin was measured in 50 patients and 13 control subjects, together with anabolic and catabolic factors. Patients were divided into two groups based on body mass index: underweight patients (n = 26) or normal weight patients (n = 24). Plasma ghrelin was significantly higher in underweight patients than in normal weight patients and healthy control subjects. Circulating tumor necrosis factor-alpha, interleukin-6, and norepinephrine were significantly higher in underweight patients than in normal weight patients. Plasma ghrelin correlated negatively with body mass index and correlated positively with catabolic factors such as tumor necrosis factor-alpha and norepinephrine. In addition, plasma ghrelin correlated positively with percent predicted residual volume and residual volume-to-total lung capacity ratio. In conclusion, plasma ghrelin was elevated in underweight patients with chronic obstructive pulmonary disease, and the level was associated with a cachectic state and abnormality of pulmonary function.