The fuels under comparison and the exhaust gas components have been briefly characterized. The pollutant emissions from vehicles powered with traditional fuels and natural gas have been compared with each other, based on the EURO 5 and EURO 6 exhaust emission standards for M1 category vehicles. The emissions from vehicles such as Fiat Panda, Volkswagen Up, Volkswagen Passat, Volkswagen Touran, and Volkswagen Caddy, according to results of type-approval tests and the EURO 5 and EURO 6 standard specifications, have been analysed. Data on noise emission levels, fuel consumption, and vehicle operation costs (fuel costs), related to feeding the vehicles with both conventional and alternative fuels and measured for individual vehicles under consideration, have been presented. According to the data, the CNG-fuelled vehicles were characterized by lower specific distance emission of carbon monoxide in comparison with the similar vehicles powered with petrol. Conversely, the vehicles fuelled with petrol showed lower specific distance emissions of hydrocarbons and nitrogen oxides as against the corresponding vehicles powered with CNG. An exception was Volkswagen Passat, for which the test results were different. For all the CNG-fuelled vehicles, the specific distance emission of carbon dioxide was lower than that measured for the similar vehicles powered with conventional fuels.