This paper analyses the factors leading to CO, emissions in the Spanish electricity generation sector in order to propose effective mitigation policies aimed at tackling those emissions. Traditionally, two broad categories of those factors have been considered in the literature: those related to the supply of electricity (technological features of the sector) and those related to the level of economic activity (demand factors). This paper focuses on an additional element, which has usually been neglected, the structural factor, which refers to the set of intersectoral transactions (related to the technologies used in other productive sectors) which connect, in either a direct or an indirect way, the general economic activity with the supply of electricity and, thus, with the emissions of the electricity generation sector. This analysis allows us to identify the so-called "sectors structurally responsible for emissions" (SSER), whose production functions involve transactions which connect the demand for goods and services with the emissions of the electricity generation sector. The methodology is based on an input-output approach and a sensitivity analysis. The paper shows that there are structural rigidities, deeply ingrained within the economic system, which lead to emissions from the electricity generation sector for which this sector cannot be held responsible. These rigidities limit the effectiveness of policies aimed at emissions mitigation in this sector. (c) 2008 Elsevier Ltd. All rights reserved.