Patients with chronic obstructive pulmonary disease (COPD) often have difficulties with keeping their weight. The aim of this investigation was to study nutritional status in hospitalised Nordic COPD patients and to investigate the association between nutritional status and long-term mortality in this patient group. In a multicentre study conducted at four university hospitals (Reykjavik, Uppsala, Tampere and Copenhagen) hospitalised patients with COPD were investigated. Patient height, weight and lung function was recorded. Health status was assessed with St. George's Hospital Respiratory Questionnaire. After 2 years, mortality data was obtained from the national registers in each country. Of the 261 patients in the study 19% where underweight (BMI <20), 41% were of normal weight (BMI 20-25), 26% were overweight (BMI 25-30) and 14% were obese. FEV(1) was lowest in the underweight and highest in the overweight group (p=0.001) whereas the prevalence of diabetes and cardio-vascular co-morbidity went the opposite direction. Of the 261 patients 49 (19%) had died within 2 years. The lowest mortality was found among the overweight patients, whereas underweight was related to increased overall mortality. The association between underweight in COPD-patients, and mortality remained significant after adjusting for possible confounders such as FEV(1) (hazard risk ratio (95% CI) 2.6 (1.3-5.2)). We conclude that COPD patients that are underweight at admission to hospital have a higher risk of dying within the next 2 years. Further studies are needed in order to show whether identifying and treating weight loss and depletion of fat-free mass (FFM) is a way forward in improving the prognosis for hospitalised COPD patients.