This paper presents an analysis of structure of portfolio of electricity generation in terms of energy security. The analysis included seven power generation technologies, for which levelized energy cost production (LEC) were calculated. These costs were calculated for each quarter of 2005–2009, taking into account fuel costs, costs of CO2 emissions and other costs (investment, capital costs, operating andmaintenance costs, decommissioning costs). For each technology risk (standard deviation) of LEC costs was calculated. Portfolios with the lowest risk for selected cheapness (inverse of costs LEC) shown in map of risk-cheapness. The analysis was carried out for three scenarios: 1) all technologies available, 2) nuclear energy not available, 3) nuclear power not available and limited production of electricity from brown coal. Calculated average cheapness and risk of portfolio correspond to current structure of electricity production in Poland. The analysis allows to draw the following conclusions: *Present structure of electricity production is inefficient in terms of risk–cheapness. There is a group of portfolios characterized by lower risk and higher cheapness. *Increasing the share of renewable energy sources in the structure of electricity production is recommended in order to reduce risk of portfolio thus increasing energy security. *Development of nuclear energy in Poland is justified in view of low risk and high cheapness. *The analysis indicates a need to increase the share of brown coal technology in production structure of electricity, which will increase energy security of Poland. *Production of electricity from natural gas and fuel oil should be kept to a minimum.