Purpose: The study was to investigate exercise capacity (peak oxygen uptake [peak VO2 ]) and pulmonary capacitance (GXcap), which is an estimate of pulmonary vascular capacitance, in patients with nonalcoholic steatohepatitis (NASH). Methods: This study utilized a database of patients with NASH (n=26 [17 male and 9 female], aged 58.9±4.3 years) and healthy individuals (n=23 [12 male and 11 female, aged 58.6±7.9 years) who underwent a maximal exercise test on a recumbent cycle ergometer (Corival; Lode) in our laboratory. During cardiopulmonary exercise tests, breathing patterns and respiratory gas exchange including breathing efficiency (VE/VCO2 ) and end-tidal CO2 (PETCO2 ) were measured. In addition, peak VO2 was obtained via averaging the last 30 seconds at peak level and GXcap was obtained by calculation as follows: GXcap=oxygen pulse (O2 pulse)×PETCO2. Results: The NASH group demonstrated reduced peak VO2 relative to the healthy group (17.5±8.4 mL/kg/min vs. 34±10.2 mL/kg/min, respectively; p＜ 0.05). In addition, there was a higher VE/VCO2 relationship in the NASH group relative to the healthy group (34.9±5.5 vs. 32.2±4.0, respectively; p＜ 0.05) and lower PETCO2 in the NASH group compared to the healthy group (32.8±4.0 mm Hg vs. 35.3±3.8 mm Hg, respectively; p＜ 0.05). Furthermore, the NASH group showed lower GXcap than the healthy group (456±150 vs. 551±202, respectively; p＜ 0.05). Conclusion Patients with NASH had reduced exercise capacity and pulmonary vascular capacitance relative to age-matched healthy adults and this may contribute to pulmonary pathophysiology in NASH.