Objective：Our aim was to investigate the QT dispersion in patients with cor pulmonale and whether the QT dispersion was affected by cardiac function and hypoxemia of the patients with cor pulmonale. Methods：Fifty-one patients with cor pulmonale and 28 age-matched normal controls underwent electrocardiography, echocardiography, and arterial blood gas analysis. The　QT　dispersion　was measured manually. Results:The QT dispersion was significantly longer in patients with cor pulmonale than those in the controls (70.1 ± 25.8 ms vs 37.6 ± 12.5 ms, P< 0.001). The QT dispersion in the patients with right heart failure was markedly longer compared with those with normal cardiac function (87.9 ± 21.6 ms vs 51.7 ± 14.2 ms, P<0.001). The QT dispersion was affected by hypoxemia. The QT dispersion in the groups of PaO2< 8 kPa　or ≥ 8 kPa was 81.0 ± 25.9 ms and 62.1 ± 21.1 ms, respectively. There was significant difference between the groups (P< 0.01). The QT dispersion was significantly correlated with the interior diameter of right ventricle in the patients with cor pulmonale (r= 0.489, P< 0.01). Conclusion: The QT dispersion may be a useful parameter in the diagnosis for cor pulmonale and in the assessment of cardiac function in the patients with cor pulmonale.