['With the alarming growth in prevalence of paediatric nonalcoholic fatty liver disease (NAFLD), there is a need for noninvasive methods of stratifying disease severity. Our aim was to evaluate a combination of serum biomarkers as a measure of disease activity in paediatric NAFLD.', 'Forty-five children with biopsy-proven NAFLD were enrolled. Caspase-cleaved CK18 fragments (CK18 M30), hyaluronic acid, leptin, and adiponectin were measured in serum using enzyme-linked immunosorbent assays and high-sensitivity C-reactive protein using a colorimetric assay.', 'Median age was 12.7 years (55% boys). Median body mass index z score was 1.7. CK18 M30 levels were significantly higher in patients with NAFLD versus controls, median 288 IU/L versus 172 IU/L (P < 0.001), and in those with steatohepatitis, median 347 IU/L versus simple steatosis (NAFLD activity score < 3), median 191 IU/L (P = 0.006). Significant fibrosis (≥F2) could be differentiated from no/minimal fibrosis (<F2), median 393 IU/L versus 243 IU/L (P = 0.03). Leptin could distinguish <F2 from ≥F2; 28.9 ng/mL versus 70.1 ng/mL (P = 0.037). Adiponectin, hyaluronic acid, and high-sensitivity C-reactive protein did not achieve significance in predicting steatohepatitis nor significant fibrosis.'] Are serum levels of CK18 M30 and leptin useful predictors of steatohepatitis and fibrosis in paediatric NAFLD?