The success of liver stiffness measurement (LSM) by transient elastography (TE, FibroScan) is influenced by anthropometric factors. In smaller adults, the M probe may fail due to narrow intercostal spaces and rib interference. We aimed to compare LSM using the FibroScan S2 (pediatric) probe with the M probe in small adults with chronic liver disease. In this prospective study, 41 liver disease patients and 18 controls with a thoracic perimeter≤ 75 cm underwent LSM using the FibroScan M and S2 probes. TE failure was defined as no valid LSMs and unreliable examinations as‹ 10 valid LSMs, an interquartile range (IQR)/LSM› 30%, or success rate‹ 60%. TE failure was not observed and reliability did not differ between the M and S2 probes (86% vs. 95%; P= 0.20). Liver stiffness measured using the M and S2 probes was highly correlated (ρ= 0.81; P‹ 0.0005) and median liver stiffness did not differ between probes (4.5 vs. 4.4 kPa; P= 0.10). However, in participants with a skin-capsular distance≥ 15 mm, median liver stiffness was higher using the S2 probe (5.5 vs. 4.9 kPa; P= 0.008). When compared with validated liver stiffness cut-offs, the S2 probe would have overestimated the stage of fibrosis compared with the M probe in 10% of patients. The FibroScan S2 probe does not improve the feasibility of LSM in adults of smaller stature and may overestimate liver stiffness compared with the M probe. The FibroScan M probe should remain the preferred tool for LSM in small adults with chronic liver disease.