Mental health problems are the leading health problems that Canadian children currently face after infancy. At any given time, 14% of children aged 4 to 17 years (over 800,000 in Canada) experience mental disorders that cause significant distress and impairment at home, at school, and in the community. Fewer than 25% of these children receive specialized treatment services. Without effective prevention or treatment, childhood problems often lead to distress and impairment throughout adulthood, with significant costs for society. Children's mental health has not received the public policy attention that is warranted by recent epidemiologic data. To address the neglect of children's mental health, a new national strategy is urgently needed. Here, we review the research evidence and suggest the following 4 public policy goals: promote healthy development for all children, prevent mental disorders to reduce the number of children affected, treat mental disorders more effectively to reduce distress and impairment, and monitor outcomes to ensure the effective and efficient use of public resources. Taken together, these goals constitute a public health strategy to improve the mental health of Canadian children.