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Intermittent priapism and increased frequency of erections have been reported with sustained release methyphenidate (OROS MPH). In two reports, symptoms were dose dependent and they emerged within a few days following MPH use and disappeared after discontinuation of the drug. Schwartz et. al. reported a 15 years-old-male with ADHD stuttering priapism associated with withdrawal of sustained-release MPH after dose increase . In this case report, a 15-year-old male, who developed after using OROS MPH excessive erections is discussed. A 15 years-old-boy was brought in for hyperactivity, irritability, attention problems, school truancy, alcohol abuse, and expulsion from school as a result of physical and verbal violence to his teacher. Although he has been treated by an other psychiatrist with olanzapine 10 mg/day and quetiapine 200mg/day for 7 months, his symptoms persisted. He was given the diagnoses of Attention Deficit Hyperactivity Disorder (ADHD) and Conduct Disorder. He was started on OROS MPH 36 mg/day (0,6 mg/kg/day) and risperidone 1mg/day. Hyperactivity symptoms showed significant improvement but irritability continued. He refused using sustained release MPH due to a sexual problem 10 days after treatment. There were approximately 3-4 erection episodes during the day, usually in the nighttime. They were spontaneous, painless and unrelated to sexual stimuli. An increase in the frequency of erections returned to normal after discontinuation of OROS MPH. He didn’t report alcohol or any other substance use within 10 days. We thought that it could be an OROS MPH-related side effect. Sublingual dopamine agonists have been used as a treatment for erectile dysfunction, and hypersexuality is a recognised side effect of subcutaneous dopamine therapy in Parkinson’s disease . Methylphenidate can lead to hypersexuality by causing the release of dopamine from the presynaptic vesicles in dopaminergic nerves. The clinicians should be aware of this side effect and counsel the children/adolescents and their families about its occurrence in order to improve the adaptation of methylphenidate treatment. Further investigation is required to understand the psychopathological mechanism of this side effect in children and adolescents.