The paper presents analysis of data obtained from tests of oil shale (OS) and peat co-combustion in a full-scale 250 MWth (useful heat output) circulating fluidized bed (CFB) boiler. The tests were conducted at nominal boiler load, with peat thermal input up to 30%. During the experiments, gas analysis was performed and ash samples were collected. The specific consumption of the oil shale and peat blend per useful heat and gross electricity was calculated and other techno-economic characteristics were determined. It was found that the co-combustion of oil shale and wet peat increased the CO emission to the level of 60 mg/Nm(3). The NOx concentration increased from 120 to 165 mg/Nm(3). The SO2 and HCl emissions remained at a very low level below 20 mg/Nm(3). A significant ash reduction, approximately 4%, was measured in the case of a 30% peat content. Due to the high peat moisture, the flue gas volume increased 5-10%. As a result of addition of peat, the content of particulate matter (PM) 10/2.5 was also lower than that by conventional oil shale CFB firing. Oil shale and peat co-combustion can be considered as a viable option and near-term solution for reducing the environmental impact of oil shale power production.