Several works have been carried out in relation to the disposal of residues from conventional coal combustion processes [1,2]. However, these residues are different from those proceeding from fluidised bed combustion systems, mainly due to the sorbent (limestone or dolomite) used to the removal Of SO2 emissions. In this paper the environmental implications [3] of the disposal of residues from fluidised bed combustion systems are studied. The procedures to evaluate the leaching behaviour of these residues have been done at three levels: shaking, column and lysimeter studies. Comparison between the three methods has been carried out, concluding that the results obtained with columns tests and lysimeter tests are very similar. So, to evaluate the environmental impact of fly ashes, it would not be necessary to do lysimeter tests (which are expensive and need a lot of time) in order to know the behaviour of ashes once they are disposed of.