In Finland the car prices are exeptionally high due to car taxes included in the new car prices. The gasoline price, which is at international leve, includes also taxes. The aim of this study was to calculate the effects of reducing the car taxes and correspondingly rising fuel taxes so that the state income car taxation does not change. The study was performed in two stages: an interview and a simulation study. The interview was aimed at the general public (postal poll) and at experts in car trade (personal interview). The aim was to reveal the parameters in the economic models explaining the behaviour of the public in car purchasing and car use. The simulation study was performed to calculate quantitative changes in, e.g. car park, traffic volumes and energy consumption caused by supposed changes in the taxation. One of the main results was that unchanged taxation is leading to rapidly increasing traffic volumes and total taxes for car use.