The paper discusses selected issues related to energy market transformations in the EU Member States. First, the main problems encountered by the EU Member States in the course of transformation are defined. They include, among others, clear defining of the energy liberalisation policy objectives and tasks, regulatory policy "democratisation," choice of a destination market model, consistent with the EU directives, but supporting changes in the local markets, too. Second, the preliminary assessment of operation of the markets hitherto was based on statistical data. The data describe present structures of energy balances of the whole EU and a few selected Member States, situated on the different stages of energy markets liberalisation, as well as the forecasted changes in these structures. Changes in the structure and volume of net imports of fuels and energy were analysed and the initial effects of the transformation process were described by dynamic analysis of energy prices and relations between them, taking into account changes in the tax policies of the EU Member States. The paper is concluded with considerations on possible trends in the energy markets and related challenges, such as fuel import dependence, diversification of supplies, competitive energy prices and environmental policy issues.