The Northern Ireland Youth Wellbeing Survey (NIYWS) was commissioned by the Health and Social Care Board (NI) with the aim of providing reliable prevalence estimates of the mental health problems of children and young people aged 2-19 years. The NIYWS used a random probability design, stratified by deprivation decile and county, to ensure even geographical distribution and representation. The survey used a broad range of validated measures to identify children and young people who met established clinical criteria for common mood, anxiety and behaviour disorders, trauma related disorders, as well as those at risk of autism spectrum disorder, eating disorders, future psychotic illness, self-injury or suicide. Data were collected on 3074 children and young people aged 2-19 years, as well as over 2800 parents. The survey achieved a high response rate (67%) and initial findings indicated that 11% of the sample were at risk of emotional or behavioural problems. The NIYWS was the first large scale nationally representative survey of the mental health of children and young people in NI. Despite the legacy of political violence the initial findings show comparable levels of emotional and behavioural problems to England.