EEM is a premier forum to discuss the development of the energy sector in a market environment. It has achieved a considerable success during the previous editions covering the electricity and gas markets policies and experiences, climate change impacts on the sector and developments at the European level.The conference comprises several sessions with keynote speakers. In each session, dealing with a certain topic, the opinions of speakers from the main European institutions, market agents and prominent academics are confronted. Following topics were covered by the keynote speakers: renewables integration, smart grids, CO 2 trading, power exchanges, offshore wind and gas markets. Those keynote sessions were alternated with parallel sessions, allowing researchers to present their work in 20-min talks.This special issue contains seven papers from the sixth International Conference on the European Energy Market, (EEM09), held at the K.U.Leuven (Belgium) on May 27-29, 2009. The papers address a variety of topics, ranging from investments in generation and transmission to demand-side integration in the energy market. The full proceedings of the conference can be found on http://ieeexplore.ieee.org/xpl/conferences.jsp#.Szolgayova et al.[1] generate distributions arising from the investment behavior optimized in a real options model, accounting for uncertainty and irreversibility at the plant level, and use them in a dynamic portfolio model, where the conditional value-at-risk is the risk measure. They illustrate that this approach is not only useful from the aggregate investment point of view but also for the purpose of evaluating the effects of policy on investment patterns and the resulting energy mix.Perekhodtsev and Baselice [2] examine the bidding behavior of Enel in 2004 to estimate the extent to which Enel was bidding opportunistically in temporal and geographic markets in which it was indispensible. This analysis has shown that over the period from April to August 2004, the bidding behavior of Enel varied across plant types. The authors verified whether this conduct could have had a material impact on market prices.Obersteiner and Saguan [3] model wind power-price interactions and investigate the sensitivity of the market value on a number of wind power and system-related parameters. Results indicate that for expected wind capacities in 2020 the market value is significantly lower than the baseload price. The market value reducing effect varies among countries and is comparably low for wind power portfolios whose generation is weakly correlated with the overall wind power generation in the respective power market.Cossent et al.[4] present a quantification of the impact of DG on distribution network costs in three real distribution areas. The computation of the distribution network costs was carried out by means of two large-scale distribution planning models called reference network models (RNMs). Van den Bosch et al. [5] analyze the present arrangements and the future requirements to be posed on incentives an...