Objectives: To assess the degree to which preventive child health professionals (CHPs) identify and manage psychosocial problems among preschool children in the general population and to determine the association with parent-reported behavioral and emotional problems, sociodemographic factors, and mental health history of children. Design: The CHPs examined the child and interviewed the parent's and child during their routine health assessments. The Child Behavior Checklist (CBCL) was completed by the parents. Setting: Sixteen child health care services across the Netherlands that routinely provided well-child care to nearly all preschool children. Patients: Of 2354 children aged 21 months to 4 years who were eligible for a routine health assessment, 2229 (94.7%) participated. Main Outcome Measures: Identification and management of psychosocial problems by CHPs. Results: In 9.4% of all children, CHPs identified psychosocial problems. Two in 5 of the CHP-identified children were referred for additional diagnosis and treatment. Identification of psychosocial problems and subsequent referral were much more likely in children with a clinical CBCL total problems score than in others (identification: 29% vs 7%; odds ratio [95% confidence interval], 5.40 [3.45-8.47]; referral: 15% vs 3%; odds ratio [95% confidence interval], 6.50 [3.69-11.46]). Conclusions: The CHPs frequently identify psychosocial problems in preschool children, although less than among school-aged children, but they miss many cases of parent-reported problems as measured by a clinical CBCL score. This general population study shows substantial room for improvement in the early identification of psychosocial problems