Background: There are many studies about predictors of mortality in patients with chronic heart failure or acute decompensated heart failure. We sought to evaluate prognostic factors in patients with first diagnosed acute heart failure, and compare between systolic heart failure (SHF) and diastolic heart failure (DHF). Methods and Results: We consecutively enrolled 460 patients who were first diagnosed as acute heart failure (aged 68 짹 13 years, 57% females). Within 24 hours, all patients underwent echocardiography, and laboratory tests including B-type natriuretic peptides (BNP). After the patients were stabilized, just before discharge, the symptom, BNP level, and echocardiographic parameters were reassessed, and 6MWT was performed. DHF (left ventricular ejection fraction (LVEF) > 40%) was present in 241 (52%) and SHF in 219 (48%). DHF was related to older age (71짹12 vs. 66짹15, P=0.001), female sex (68% vs. 53%, P<0.0001), history of hypertension (64% vs. 44%, P<0.0001), and lower levels of BNP (950 짹988 vs. 1653 짹1372 pg/mL, P<0.0001) and 6 minute walk test (488짹 195 vs. 589짹 194 m) as compared with SHF. During a median follow-up time of 658 days, all-cause mortality was 39% and showed no significant difference between SHF and DHF. In univariate analysis, age, body mass index, glucose, use of beta blocker at discharge, and use of angiotensin converting enzyme (ACE) inhibitor at discharge were associated with all-cause mortality, but LVEF or 6 minute walk test was not. By multivariate analysis with adjustment of age and BNP, beta blocker use at discharge was an independent predictor of mortality (Odds ratio (OR) 2.1; 95% confidence intervals (CI) 1.3 to 3.3, P=0.02). In subgroup analysis (SHF and DHF respectively), beta blocker use at discharge was significantly associated with all-cause mortality only in DHF (OR 2.8; 95% CI 1.5 to 5.1, p=0.001), whereas ACE inhibitor use at discharge was an independent risk factor of mortality in SHF (OR 2.6; 95% CI 1.3 to 5.0, P=0.004). Conclusion: Our study showed that patients with DHF among first diagnosed acute heart failure had a similar poor prognosis to SHF in spite of difference of LVEF and BNP level between two groups. Beta blocker at discharge was the most important factor of mortality for all fresh heart failure patients. Further study is required to evaluate a putative role of beta blocker in reducing mortality of first diagnosed DHF or SHF.