The study compared clinical characteristics and prognosis in patients with HBV-ACLF (acute liver failure of chronic hepatitis B) and ALD-ACLF (acute liver failure of alcoholic etiology), including 83 patients in each group. Patients with ALD-ACLF had a higher proportion of males, more frequent ascites, and higher levels of white blood cells (WBC), neutrophils, and monocytes, but lower levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), albumin (ALB), potassium (K), and sodium (Na) than HBV-ACLF patients (all differences with P < 0.05). Prognostic factors for 90-day mortality were total bilirubin (TBIL) and prothrombin time (PT) in HBV-ACLF, whereas in ALD-ACLF they were WBC, TBIL and PT. There were no significant differences in the 90-day prognosis between the two groups. The findings require validation in multicenter studies with larger samples.