The mercury and maceral content of subbituminous feed coals burned at six Canadian power plants was measured and compared to the mercury and carbon content of corresponding fly ashes. The fly ashes were collected from electrostatic precipitator (ESP) pollution controls used at the power plants. Four feed coals from the Upper Cretaceous to Tertiary age Scollard Formation were deposited in freshwater depositional environment and contain 35-44% inertinite. Two feed coals from the Upper Cretaceous age Horseshoe Canyon Formation were deposited in a brackish water environment and contain 14% inertinite. The data show that abundant inertinite equates to more unburned carbon in ESP fly ash, and to enhanced capture of mercury in cold-side ESP fly ash. This indicates that the inertinite content of a coal seam may be indicative of the percentage of unburned carbon and the percentage of mercury captured by a cold-side ESP. (C) 2004 Elsevier B.V. All rights reserved.