OBJECTIVE:Standardised developmental screening tools are important for the evaluation and management of developmental disorders in children with CHD; however, psychometric properties and clinical utility of screening tools, such as the Ages & Stages Questionnaires, Third Edition (ASQ-3), have not been examined in the CHD population. We hypothesised that the ASQ-3 would be clinically useful for this population. Study design ASQ-3 developmental classifications for 163 children with CHD at 6, 12, 24, and/or 36 months of age were compared with those obtained from concurrent developmental testing with the Bayley Scales of Infant and Toddler Development, Third Edition. RESULTS:When ASQ-3 screening failure was defined as ⩾1 SD below the normative mean, specificity (⩾81.9%) and negative predictive value (⩾81.0%) were high across ASQ-3 areas. Sensitivity was high for gross motor skills (79.6%), increased with age for communication (35.7-100%), and generally decreased with age for problem solving (73.1-50.0%). When ASQ-3 screening failure was defined as ⩾2 SD below the normative mean, specificity (⩾93.6%) and positive predictive value (⩾74.5%) were generally high across ASQ-3 areas, but sensitivity was low (31.1%) to fair (62.8%). The ASQ-3 showed improved accuracy in predicting delays over clinical risk factors alone. CONCLUSIONS:The ASQ-3 appears to be a clinically useful tool for screening development in children with CHD, although its utility varied on the basis of developmental area and time point. Clinicians are encouraged to refer children scoring ⩾1 SD below the normative mean on any ASQ-3 area for formal developmental evaluation.