In this study we included 155 subjects, 35 patients with left heart failure, 49 chronic obstructive pulmonary disease (COPD)-cor pulmonale, 26 COPD, 20 pulmonary embolism and 25 healthy subjects. Plasma BNP level in patient with left heart failure was significantly higher than COPD-cor pulmonale, COPD and control subject in respect 1167 +/- 746, 434 +/- 55, 32 +/- 36 and 32 +/- 12 pg/mL. Plasma BNP in group of cor pulmonale was higher than COPD and control subject 434 +/- 55 vs. 32 +/- 12 pg/mL. There were no difference between COPD and control subject 32 +/- 36 vs. 32 +/- 12 pg/mL. In pulmonary embolism BNP was higher than controls 357 +/- 391 vs. 32 +/- 12 pg/mL and BNP levels of massive pulmonary embolism was higher non-massive embolism 699 +/- 394 vs 166 +/- 213 pg/mL. In this study BNP levels negative correlated with EF and positive correlated with pulmonary artery pressure. We suggest that increased BNP levels are correlated with ventricular failure and BNP is diagnostic and prognostic marker of heart failure and increased right ventricular pressure contributes to elevated BNP in patients with PE.