Coal-fired power plants produce fly and bottom ash that contains a complex mixture of organic and inorganic compounds, including rare earth elements (REEs). Our research analyzed eight samples of coal combustion residuals to characterize and determine the mode of occurrence of REEs. Our findings show that REEs are present mostly in the form of oxides and hydroxides, with concentrations varying based on the coal source and combustion conditions. Understanding the composition and distribution of REEs in coal combustion residuals is essential for developing strategies to recover these critical elements and minimize environmental impacts.