Lignin is one of three components that make up wood, and it is the most recalcitrant among these compounds due to its highly degradation-resistant phenolic polymer structure. Lignin is composed of carbon, oxygen and hydrogen, which has the potential to be a feedstock for biofuels and biorefining processes. In this work, lignin was depolymerized to produce succinic and acetic acids via a photocatalytic reaction. TiO2 and H2O2 under UV-light were used as a photocatalyst and photocatalyst promoter, respectively. The effect of TiO2 and H2O2 dosage, solution pH and reaction time on %yield of dicarboxylic acid was determined. Optimization of reaction conditions was done with response surface methodology using a Box-Behnken design. It was found that the maximum %yield of succinic acid (7.8%) was at a reaction time of 24 h, a 2.37 g/l of TiO2 dosage and 25.45 μl of H2O2 dosage and pH 7.0. The predicted dicarboxylic acid yield using was accurate with R2=91.8%. This would be an alternative way to produce high-value fine chemicals from lignin.