OBJECTIVES: The aim of the study was to estimate the prevalence of child and adolescent mental health problems in Siberia and to investigate the effects of psychosocial factors. STUDY DESIGN: A cross-sectional study with the stratified randomised sample of schoolchildren provided prevalence estimates. Second study involved 1,382 adolescent self-reports and 1,864 parent reports of three through 17 year old children. METHODS: Psychopathology measure was the Strengths and Difficulties Questionnaire, in the first study it was supplemented by psychiatric assessment. Psychosocial factors included measures of child close and distant environment. RESULTS: Prevalence of psychiatric disorder in Siberian children is around 15-20%; emotional and behavioural disorders are the two most common categories. Psychosocial factors explained around 15% of internalising problems, and up to 30% of externalising problems. Harsh parenting was a risk factor; intact family, parent’s education, family cohesion and safe neighbourhood contributed to the lower level of problems. CONCLUSIONS: The rate of child psychiatric problems in Siberia is higher than in the developed countries; the type of the problems is similar to other countries. Life style factors were more powerful predictors than measures of socio-economic status. Prevention should be aimed at identified risk factors and disadvantaged children.