MIF is a pluripotent cytokine associated with several different inflammatory conditions, but its role within lung inflammation and COPD is unclear. This study aimed to examine MIF in both stable COPD and during acute exacerbations (AECOPD). The study included 433 patients with COPD aged 41-76 and 325 controls from the Bergen COPD cohort study. All patients had a FEV1 <80% predicted, FEV1/FVC ratio <0.7 and a smoking history >10 packyears. Serum levels of MIF were compared between the two groups at baseline, and for 149 patients measurements were also done during AECOPD. Linear regression models were fitted with MIF as the outcome variable, adjusted for sex, age, body composition, smoking and Charlson Comorbidity Score (CCS). Median MIF (IQR) in COPD patients was 20.1 (13.5-30.9) compared to 14.9 (11.1-21.6) in controls (p<0.01). MIF was bivariately associated with sex, body composition and CCS (p<0.05 for all). In the regression analysis, MIF was significantly higher in COPD-patients, coefficient 1.32 (p<0.01) and 1.30 (p<0.01) unadjusted and adjusted respectively. In addition, in 146 patients at AECOPD, MIF was significantly elevated, with median 23.2 (14.1-42.3) compared to measures at stable disease 19.3 (12.4-31.3), p<0.01. Serum levels of MIF were significantly higher in COPD patients compared with controls. We also identified an additional increase in MIF-levels at AECOPD.