A novel procedure based on ultrasound-assisted oxidative desulfurization was applied for diesel oil treatment, which was performed simultaneously to ultrasound-assisted oxidative denitrogenation (UAODN) in order to minimize N interference over S oxidation. The effect of ultrasonic irradiation time, reagent amount and the nature of extraction solvent were evaluated. A petroleum product feedstock containing quinoline was used as a model nitrogen compound and acetic acid and hydrogen peroxide were used as oxidizing agents. Nitrogen removal above 95% was obtained for the model oil after 5 min of ultrasonic irradiation (20 kHz, 750 W, 40%). Additionally, this study showed that quinoline can reduce the oxidative desulfurization efficiency of an oil containing dibenzothiophene. The application of oxidative treatment without ultrasound showed that nitrogen and sulfur removal efficiencies for five diesel oil samples were considerably lower (lower than 22 and 40% for nitrogen and sulfur, respectively). The UAODN procedure was applied for the treatment of a hydrotreated petroleum product feedstock and samples of diesel oil with nitrogen and sulfur content up to 226 and 375 mg kg(-1), respectively. Under optimized conditions, nitrogen content below 20 mg kg(-1) was obtained and the feasibility of ultrasound for simultaneous denitrogenation and desulfurization was demonstrated. (C) 2014 Elsevier B.V. All rights reserved.