N-terminal pro-brain natriuretic peptide (NT-proBNP) is a pro-hormone, secreted by the myocardium in response to various stimuli, was found to be correlated with some hemodynamic parameters in pulmonary arterial hypertension (PAH). We investigated plasma NT-proBNP levels and the relationships between NT-proBNP and some hemodynamic parameters in chronic obstructive pulmonary disease (COPD) patients with or without PAH. We found that plasma NT-proBNP level was significantly lower in PAH group compared with the control group (4982.5 ± 22.5 pg/ml vs 5067.5 ± 21.8 pg/ml, P < 0.05). In the study population, only fasting insulin level was found to be positively correlated with fasting NT-proBNP level and only fasting insulin was an independent predictor of NT-proBNP (standardized coefficient = 0.708, P < 0.001) in a multiple regression model analysis. In the PAH group, only fasting insulin was found to be positively correlated with NT-proBNP, whereas other parameters were not found to be correlated with NT-proBNP. Our data suggests that the expression of NT-proBNP might be different in different kinds of pulmonary hypertension.