This paper presents the analysis and comparison of energy and environmental properties of various city bus systems: diesel and compressed natural gas internal combustion engines, trolleybus, and battery electric bus. It is based on experimental research on fuel and energy consumption of city buses with aforementioned propulsion systems carried out under similar driving conditions – on the same city bus lines in Belgrade and Novi Sad, and on evaluation of energy efficiency and CO2 emission of real electricity production in Serbia. In this way, “tank-to-wheel” and “well-to-wheel” energy consumption and CO2 emissions of considered bus driving systems have been evaluated and compared. The results show all complexity of the matter since benefits of application of different systems largely depends on bus exploitation conditions and even more of the conditions of electric energy production. The compressed natural gas internal combustion engine compared to the Diesel engine provides obviously benefit in harmful gas emissions. However, CO2 emissions are on a similar level, while energy efficiency is even less. Electric propulsion systems provide undoubtedly benefit in energy consumption, harmful gases and CO2 emissions if tank-to-wheel conditions are considered, but well-to-wheel characteristics strongly depend on the condition of electric energy production.