Objective: Despite increasing incidence, data regarding clinical and demographic characteristics of patients with acute heart failure (AHF) admitted to cardiac intensive care unit (ICU) are inconclusive. The aim of this study was to assess the presentation characteristics and factors determining the length of hospital stay in this particular patient population. Methods: We conducted a single-center, prospective study involving 150 patients hospitalized to cardiac ICU with the primary diagnosis of AHF. Chi-square and Student t tests were used for the analysis of categorical and continuous variables, respectively. Linear regression analysis (LRA) was used to determine the factors affecting the length of hospital stay. Results: Forty-nine percent of the patients had new-onset AHF and 25% had preserved left ventricular ejection fraction (LVEF). In 25.3% of all patients and 46.6% of the patients with new-onset HF the precipitating factor was acute coronary syndrome. Atrial fibrillation and valvular heart disease as precipitating factors were more common in patients with preserved EF, when compared to low EF group. LRA showed that presence of anemia [β=1.62; 95% CI 0.08-3.15; p=0.039)] and severe mitral regurgitation (β=2.55; 95% CI 0.06-5.05; p=0.045) and systolic blood pressure (β=-0.03; 95% CI -0.06 - -0.002; p=0.039) and blood urea nitrogen (β=0.034; 95% CI 0.006 - 0.06; p=0.016) were the independent predictors of length of stay. Conclusion: Underlying cardiovascular risk factors, comorbidities and precipitating pathologies were diverse and highlighted the inhomogeneous characteristics of AHF syndromes. However, in-hospital mortality was high and initial clinical presentation characteristics were significantly associated with in-hospital outcome.