OBJECTIVES: To identify the prevalence of stimulant and antidepressant medication use by children and adolescents with symptoms meeting the criteria for attention-deficit/hyperactivity disorder (ADHD) and major depressive disorder (MDD) in Australia. To identify factors associated with stimulant and antidepressant use by children and adolescents in Australia. METHODS: Data are from a nationally representative sample of 4- to 17-year-olds (n = 6310). Parents completed the Diagnostic Interview Schedule for Children-Version IV (DISC-IV) and the Strengths and Difficulties Questionnaire. Eleven- to 17-year-olds completed a self-report version of the DISC-IV MDD module. Interviewers recorded prescribed medications used by participants in the previous 2 weeks. RESULTS: During a 2-week period, 1.3% of all 4- to 17-year-olds and 13.7% of those with symptoms meeting the criteria for ADHD had used stimulant medication, while 0.9% of all 4- to 17-year-olds and 13.4% with MDD had used antidepressants. In total, 22.6% of those using stimulant medications and 57.7% using antidepressant medications did not have symptoms meeting criteria for ADHD or MDD, respectively. Among 11- to 17-year-olds, 5.6% of those with adolescent-only-reported MDD, 10.9% of those with parent/carer-only-reported MDD, and 25.7% of those with MDD reported by both parents/carers and adolescents were using antidepressant medications. CONCLUSIONS: Only a minority of 4- to 17-year-olds with ADHD and MDD were being treated with stimulant or antidepressant medication. The percentage of adolescents with MDD using antidepressant medications varied depending on whether adolescents, parents/carers, or both identified the presence of MDD. This highlights the importance of using information from both these informants when assessing and treating adolescent depressive disorder.