Background It is known that the main role of D-dimer has been as an exclusionary test in patients with suspected venous thromboembolism.However,the D-dimer is increasingly beginning to find clinical utility as a marker in the evaluation of the extent of the embolic disease.The aim of the study was to determine whether D-dimer levels predict the radiological markers of pulmonary embolism (PE) severity using Mastora score.Methods This prospective study involved 69 patients with acute PE proved by computed tomography pulmonary angiography (CTPA).The D-dimer level was noted.A pulmonary artery obstruction index (PAOI; Mastora score) ≥21.3％ indicated severe obstruction of PE.A right ventricle/left ventricle (RV/LV) ratio ＞0.9 indicated RV dysfunction.Results The median D-dimer level and PAOI were 765 μg/L (95％ C/:750-1 205 μg/L) and 16.77％ (95％ CI:16.32％-23.06％),respectively.The D-dimer level was positively correlated with PAOI (r=0.417,P ＜0.000 1).PAOI ≥21.3％ was associated with high D-dimer levels (median,993 μg/L (95％ C/:856-1 841 μg/L),Z=-2.991,P=0.003).The D-dimer level was correlated with the RV/LV ratio (r=0.272,P=0.024).RV/LV ratios ＞0.9 were associated with high D-dimer levels (median,880 μg/L (95％ CI:764-1 360 μg/L),Z=-2.070,P=0.038).PAOI was positively correlated with the RV/LV ratio (r =0.390,P=0.001).After three months,both the PAOI and D-dimer levels decreased (Z=-7.009,P ＜0.000 1; Z=-6.976,P＜0.000 1,respectively).Conclusion D-dimer levels are positively correlated with PE burden and right ventricle dysfunction on CTPA,and can help monitor the therapeutic response.