Spatial construction skills were assessed in children with left (LH) or right (RH) hemisphere focal brain injury and control children. Children copied simple and complex block models which were rated on accuracy and spatial strategy. The accuracy of simple and complex constructions for 4- to 5-year-old children with LH injury was indistinguishable from 4-year-old controls. However, although they were able to produce accurate complex constructions, the processes used by children with LH injury differed from those of normal children. On both simple and complex constructions, 4- to 5-year-old children with RH injury showed evidence of developmental delay. For both accuracy and process measures, children with RH injury performed at a level comparable to normal children at 3 years. A second group of children with LH and RH injury were tested at 5 to 6 years of age. Both lesion groups were indistinguishable from 4-year-old controls in terms of accuracy. However, both children with LH and RH injury used different spatial processes than did controls. This study emphasizes the importance of distinguishing between products of behavior and the processes which underlie them. It is in the dissociation of products and process of behavior that the subtle spatial construction deficits in this population of brain-injured subjects is revealed.