Diastolic and systolic heart failure (DHF and SHF) are the different clinical subsets. Because many heart failure patients have sleep apnea syndrome (SAS), oxygen supply improves the patient’s prognosis. Thus, the purpose of this study was to compare the effects of oxygen treatment for premature ventricular contractions (PVCs) suppression in patients between DHF and SHF. Patients with heart failure (BNP>80 pg/ml), SAS (AHI> 5) and frequent PVCs (>30/h) were admitted to the hospital for at least 2 consecutive nights. On the first night, the respiratory and Holter monitoring was performed without nasal oxygen treatment; the same monitor with nasal oxygen therapy (3 L/min) was performed on the second night.The DHF patients (more than 40% of LVEF, n=7) showed a significant decline of PVC numbers (63.1 ± 33.0% post/pre) compared to those (119.8 ± 45.3% post/pre, p<0.05) of the SHF patients (less than 40% of LVEF, n=8) by the oxygen treatment. The DHF patients also showed higher SDNN (253.0 ± 260.0 ms) levels compared to those of SHF patients (52.9 ± 22.4 ms, p<0.05). However, AHI and BNP levels were compatible between the two groups.