The preparation, optimization and activity of active absorbent prepared from oil palm ash for the removal of SO2 in flue gas from combustion systems were investigated. The absorbent was prepared from oil palm ash, calcium hydroxide and calcium sulfate using a water hydration process. A Central Composite Design (CCD) was used to study the influence of various absorbent preparation variables - hydration period, amount of oil palm ash, and amount of CaSO4 - on the BET (Brunauer-Emmett-Teller) specific surface area of the resulting absorbent. The surface areas of the absorbents obtained were in the range of 18.7-147.2 m(2)/g. It was found that all three absorbent preparation variables studied have a significant positive influence on the BET surface area of the resulting absorbent. An empirical model was then developed to correlate the three absorbent preparation variables to the BET surface area of the resulting absorbent. The model showed significance at a confidence level of 95 % using Analysis of Variance (ANOVA). Based on the empirical model, a maximum specific surface area of 128.6 m(2)/g exists within the range of the experimental variables investigated. The hydration conditions that result in the maximum surface area are a hydration period of 10 h, amount of oil palm ash 15.0 g, and amount of CaSO4 2.7 g. Experimental validations of these predicted optimum hydration conditions gave surface areas in the range of 125.9-129.5 m(2)/g. These results are in excellent agreement with the predicted value. In addition, desulfurization activity tests showed that the absorbent derived from oil palm ash/Ca(OH)(2)/CaSO4 exhibited a higher desulfurization capacity compared to its starting materials.