Behavioural and emotional problems in Finnish three-year-olds was studied using the Child Behavior Checklist for ages 2-3 as a standardised rating scale at well-baby clinics in two cities in Finland. Altogether 374 questionnaires were analysed which is 71% of the target population. When compared with studies from other countries the mean scores and prevalences of preschool children's problem behaviours were rather similar. Boys were reported to be more destructive than girls. Parental education level, living in one-parent family and parental unemployment were associated with a higher level of problem behaviours. No significant differences were found in emotional or behavioural problems related to the child's day care. Co-sleeping with parents was associated with sleep problems.