This work detailed in this study utilized 20 kHz ultrasonic irradiation as a mechanism of hydrogen peroxide production. The effects of various operating parameters were investigated, including ultrasonic intensity, solution pH, source of water, initial dibutyl phthalate concentration and the presence of hydrogen peroxide. During the irradiation, the H₂O₂ concentration arising was monitored. The results indicate that H₂O₂ is produced by cavitation during ultrasonic irradiation. An increase in ultrasonic intensity increases the amount of hydrogen peroxide produced. The initial pH of the solution does not affect the efficiency of processes substantially. H₂O₂ is regarded as one of the most effective additives enhancing the sonochemical production of hydroxyl radicals and hydrogen peroxide, but too high a dose is known to exert a negative effect. Above a 0.1 mM dose of H₂O₂, the amount of H₂O₂ formed decreased as the concentration of H₂O₂ increased. Thus, the concentration of hydrogen peroxide plays a crucial role in the extent to which effectiveness of the combined process is enhanced. The negative effect on reactions of the presence of additional components in the reaction solution was also confirmed. It was therefore concluded that experimental evaluation of optimum parameters of hybrid processes is a matter of importance.