The purpose of this study was to identify the relationship between nutritional status and the severity of the disease in patients with COPD in South Korea. This study used pretest data from a larger intervention study. Data were collected from March to October 2010, and 251 patients diagnosed with COPD from five hospitals in South Korea were included in the analysis. All participants were interviewed face-to-face. Actual dietary intake was measured by a 24-h dietary recall, and the body mass index (BMI), obstruction of the airway (FEV1% predicted), degree of dyspnea (modified Medical Research Council: MMRC), and exercise capacity (6 min walking distance: 6MWD) (BODE) index was calculated to estimate the severity of the condition. Lower BODE index scores indicate lower risk of mortality. The data were analyzed by descriptive statistics, a chi(2) test, t-tests, analysis of variance (ANOVA), Pearson correlation, and hierarchical multiple regression using SPSS 18.0. The mean age of the participants was 66.83 years and 92.4% of the participants were men. The mean total energy intake was 1431.65 kcal, and the mean BODE index score was 2.89. Total energy intake significantly explained additional variance in BODE, BMI, the severity of the perceived dyspnea, and the length of 6 min walk after controlling for age, duration after diagnosed with COPD, and physical activities. The findings of this study emphasized the importance of calorie intake in the disease severity among COPD patients. Further research on the effects of nutritional intervention on the health outcomes of patients with COPD is warranted. (C) 2013 Published by Elsevier Ireland Ltd.