A density separation method was used to reduce ash components, which form fireside deposits during coal combustion, as well as trace elements, in a Greek lignite. Standard techniques were applied to predict the slagging and fouling propensity of clean coal and to determine the trace elements concentration in this. Deposition tendencies were estimated through the use of empirical indices for lignitic type ashes. Significant reductions in ash content (up to 60%) were achieved by dense liquid separation of the lignite. Coal cleaning diminished the slagging and fouling potential of the feed, reflecting some alterations in the chemistry and mineralogy of the ash-forming components. The ash of beneficiated materials was richer in the basic oxides, while poorer in quartz. Also, the ash fusion temperatures (initial deformation and hemispherical) were significantly increased, though the contents of quartz and anhydrite remained high. Most trace elements were found to be associated with the mineral phase. Removal efficiency was low by the density separation method, but the environmental impact of these elements is anticipated to be negligible.