AIM To evaluate the differences in acute kidney injury (AKI) between acute-on-chronic liver failure (ACLF) and decompensated cirrhosis (DC) patients. METHODS During the period from December 2015 to July 2017, 280 patients with hepatitis B virus (HBV)-related ACLF (HBV-ACLF) and 132 patients with HBV-related DC (HBV-DC) who were admitted to our center were recruited consecutively into an observational study. Urine specimens were collected from all subjects and the levels of five urinary tubular injury biomarkers were detected, including neutrophil gelatinase-associated lipocalin (NGAL), interleukin-18 (IL-18), liver-type fatty acid binding protein (L-FABP), cystatin C (CysC), and kidney injury molecule-1 (KIM-1). Simultaneously, the patient demographics, occurrence and progression of AKI, and response to terlipressin therapy were recorded. All patients were followed up for 3 mo or until death after enrollment. RESULTS AKI occurred in 71 and 28 of HBV-ACLF and HBV-DC patients, respectively (25.4% vs 21.2%, P = 0.358). Among all patients, the levels of four urinary biomarkers (NGAL, CysC, L-FABP, IL-18) were significantly elevated in patients with HBV-ACLF and AKI (ACLF-AKI), compared with that in patients with HBV-DC and AKI (DC-AKI) or those without AKI. There was a higher proportion of patients with AKI progression in ACLF-AKI patients than in DC-AKI patients (49.3% vs 17.9%, P = 0.013). Fortythree patients with ACLF-AKI and 19 patients with DC-AKI were treated with terlipressin. The response rate of ACLF-AKI patients was significantly lower than that of patients with DC-AKI (32.6% vs 57.9%, P = 0.018). Furthermore, patients with ACLF-AKI had the lowest 90 d survival rates among all groups (P < 0.001). CONCLUSION AKI in ACLF patients is more likely associated with structural kidney injury, and is more progressive, with a poorer response to terlipressin treatment and a worse prognosis than that in DC patients.