The aim of this study is to investigate the contribution of fly ash from lignite-fired power stations to the air pollution of the Western Macedonia region of northern Greece. Several filters that capture airborne particles were collected over a year's period (March 2003 to February 2004), from seven sampling sites spread throughout the area. In addition, fly ash was collected from two power plants in this area along with stack ash (fly ash that escaped the electrostatic precipitators and trapped at the stack's exit). Both fly ash and filters were analysed with the help of Environmental Scanning Electron Microscopy (ESEM), coupled with energy dispersive X-ray analysis (EDX) in order to determine the morphological, mineralogical and chemical characteristics of fly ash particles. Cenospheres, vesicular spheres, spheroids, dense spheres and chars were the main recognized fly ash particles. Similar airborne particles were also present in almost every filter collected in the area. Sampling sites situated nearby power plants had apparently more fly ash particles. Fine fly ash particles (<5 mu m) were transported to distant sites, while larger fly ash particles (>= 10 mu m) were mostly recorded in the vicinity of power stations. The analysis also revealed the presence of potential toxic elements in the fly ash, a fact with important environmental implications. (C) 2007 Elsevier B.V. All rights reserved.