Objective: The aim of this study was to investigate medication persistence in Turkish children and adolescents with attention-deficit/hyperactivity disorder (ADHD). The effects of sociodemographic characteristics, symptom severity of ADHD, comorbidity, and treatment-related factors influencing medication persistence in children diagnosed with ADHD were studied. Methods: Medication persistence over a continuous 12 month period was evaluated for 877 children and adolescents between 6 and 18 years of age, who were diagnosed with ADHD for the first time and started to receive medication. Medication persistence was determined according to whether or not taking the prescribed medication continued for 12 months after the initiation of treatment. Whereas the symptom severity of ADHD was assessed by using the Turgay Diagnostic and Statistical Manual of Mental Disorders, 4th ed. (DSM-IV)-based Child and Adolescent Behaviour Disorders Screening and Rating Scale-Parents Form (T-DSM-IV-S), perceived medication efficacy after the first treatment was evaluated by the Clinical Global Impressions-Improvement Scale (CGI-I). Results: In this study, medication persistence over a continuous 12 month period occurred at a rate of 30.2% (n=265) in the subjects studied. The hierarchical regression analysis conducted in this research revealed that younger age, higher hyperactivity/impulsivity symptom severity, use of long-acting methylphenidate, addition of another ADHD medication, addition of other psychotropic medications, absence of side effects, and perceived medication efficacy were associated with successful medication persistence over a continuous 12 month period. Conclusions: Understanding the factors that affect medication persistence in ADHD may improve treatment efficacy and symptom control, while minimizing future risks.