The present work reports experimental results on the determination of laminar flame velocities of hydrogen–air mixtures diluted or not by a mixture containing helium and carbon dioxide. The experimental setup consists of a spherical bomb coupled to a schlieren system and a high speed camera. The Markstein numbers are determined for all the investigated mixtures and are compared to the available literature data. Computed laminar flame velocities are obtained using PREMIX and CHEMKIN codes. Two different kinetic mechanisms are used, and the computed values are compared to the experimental ones.