The aim of this study was to examine the validation of the Hooper Visual Organization Test (HVOT) for use in children by testing for item fit, unidimensionality, item hierarchy, reliability, and screening capacity. A modified scoring system was devised for the HVOT so that children received some credit for being able to describe the function of objects. The HVOT was administered to 630 typically developing school-aged children and 210 children with Down syndrome matched for age and education. Rasch analysis and receiver operating characteristic curve were applied. Rasch analysis of data from typically developing children showed that twelve items were candidates for deletion due to poor fit to the Rasch model, violation of normality and age-related item bias. Removing these items resulted in a shortened version with 18 items that forms a reliable and strong unidimensional, hierarchical scale. The items were well targeted to the ability level of the children tested. Area under the curve for HVOT-18 was 0.84, indicating very good ability to identify visual integration deficit in children with Down syndrome. The 18-item HVOT can be summed to produce an overall index of visual synthetic ability. Subsequent work is needed to validate its use in other childhood disabilities. (Contains 2 figures and 1 table.)