Water is an indispensable resource for all aspects of life we know. However, quantities of good-quality water are limited and water pollution has become a problem we face daily. One type of pollutants of scientific and public interest are phthalates. Phthalates are esters of phthalic acid. They are widely used in various products, most commonly in plastics. Conventional methods of water treatment are inefficient in complete removal of phthalates; therefore, it is necessary to develop new, more effective approaches. An approach that has high potential for phthalates removal is application of advanced oxidation. The advantage of advanced oxidation processes is in the formation of highly reactive radical species that effectively degrade organic pollutants. The pollutants are commonly degraded to carbon dioxide and water, which is followed by reduction of toxicity and increased biodegradability of the treated water. The aim of this work was to develop and validate the method for the determination of diisobutyl phthalate. Afterwards, the kinetics of photooxidative degradation of phthalates was determined. Validation included determination of further parameters: linearity, limit of detection, limit of quantification, accuracy and precision with confidence of 95%. Photooxidations were performed using hydrogen peroxide and sodium persulfate. Pseudofirst- order kinetics was determined. Photooxidation process using hydrogen peroxide resulted in better degradation.