The introduction of carbon tax is expected to mitigate GHG emissions cost-effectively. With this expectation identifying the impacts of carbon tax on energy demand and GHG emission reductions is an interesting issue. One of the basic methods of estimating these impacts is using the price elasticity. There are, however, some unanswered questions regarding the use of price elasticity. First, which elasticity estimates are appropriate to measure the impacts of carbon tax on energy demand? The existing estimates are estimated in the presence of a substitute. To assess the impact of carbon tax could we use these estimates? Second, how can we compromise the differences among the existing estimates depending on estimation methods and specifications? For example, how can we accommodate the difference in the estimates from the regional panel specification and the aggregate specification? This paper tries to answer these questions with the price elasticity of gasoline demand. With an appropriate price elasticity, we show how much gasoline consumption and GHG emissions are reduced by carbon tax for different scenarios of carbon tax rate. (C) 2010 Elsevier Ltd. All rights reserved.