The project starts from the results of a research project previously carried out by CRF, AVL and POLITO on a DI NG engine. The first phase is concerned with the calibration of 1D predictive simulation models for the reference engine and it is performance-oriented; in the second phase the influence of the change from NG to H2 fuelling is considered, by contemplating1D analysis, with a particular focus on injection, mixing and combustion processes. From the analyses carried out, by keeping a stoichiometric air-fuel ratio for both CNG and hydrogen, an increase of about 2.5% in torque, power and bmep hasbeen recorded.