This research describes methods for the sequential determination of Pb-210 and Po-210 activity concentrations in Ca-rich ash samples collected from oil shale-fired power plants in Estonia. The procedure involves digestion of Ca-rich ash samples in a microwave digestion system, radiochemical separation of Pb-210 and Po-210 and their measurements. All samples, blanks and standards were measured by liquid scintillation counting (Quantulus 1220). The method was tested using IAEA (International Atomic Energy Agency) RGU-1 and IAEA-444 reference materials. Spectral calibration/peak identification which included the optimization of alpha/beta discrimination system (pulse shape analyser), and recovery have been made by Po-209 and Pb-210 standard solutions.