Abstract: AIM To investigate the similarities and differences in left ventricular structures and left ventricular systolic functions between heart failure patients with preserved ejection fraction (HFpEF) or reduced ejection fraction (HFrEF). METHODS Forty HFpEF patients and 40 HFrEF patients were included in the study. Echocardiograghy was performed. Left ventricular systolic function indices including left ventricular ejection fraction (LVEF), peak ejection rate (PER) and peak ejection time (TPER) were measured using radionuclide ventriculography under resting condition and dobutamine stress. The maximal change rate (MCR) of HR, LVEF, PER and TPER were calculated. The 6-month mortality rate in HFpEF patients and HFrEF patients was recorded. LVEF in survivors of HFpEF patients was measured after 6 months. RESULTS LAD, LVESD and LVEDD in HFpEF patients were much lower than in HFrEF patients (P<0.05). IVST and LVPWT in HFpEF patients were higher than in HFrEF patients (P<0.05). LVEF at rest and dobutamine stress in HFpEF patients was higher than in HFrEF patients (P<0.05). There were no significant differences in MCR of LVEF, PER, TPER and 6-month mortality rate between groups. Three out of 34 (9%) survivors with HFpEF developed HFrEF in 6 months. CONCLUSION Significant difference in left atrial and ventricular structures is observed between HFpEF patients and HFrEF patients. LVEF at rest and stress in HFpEF patients was higher than in HFrEF patients. There is no significant difference in contractile reserve. Some HFpEF patients may develop HFrEF.