Automotive industry is focused on CO2 emission reduction, and the emission is dependent on fuel consumption. Better fuel economy can be achieved by increasing the efficiency of internal combustion engines by implementing cylinder deactivation. This technology achieves the fuel consumption benefit by firing only some of the cylinders when the engine load is low. Modern trend in automotive industry is hybridisation. A hybrid powertrain allows fuel consumption to be further reduced by adding a motor/generator. Deactivating some of the cylinders leads to higher vibration that can be compensated by torque generated by the electric motor. The aim of the thesis is to create a methodology for dynamic simulations of mild-hybrid powertrain with cylinder deactivation and to assess the benefit of using torque smoothing in this kind of powertrain. The results are obtained by dynamic simulations of hybrid powertrain and verified by available experiments.