Epidemiological studies have characterized the high burden of suffering that child psychiatric disorders cause--14% of children (1.1 million in Canada) have clinically important disorders at any given time. In this review, we summarize the recent research and discuss several unresolved scientific issues that must be addressed to make epidemiology more useful to policy-makers. We then discuss implications for policy-making to improve children's mental health outcomes. Overall, given the high prevalence rates, increasing clinical services alone will not suffice; rather, a multifaceted mix of strategies is required.