This review discusses recent advances in our understanding of the genetic basis of child psychiatric disorders. As in adult psychiatry, progress in this area has been slow. First, it now appears clearer than ever that the "one gene, one disease" model is inappropriate for the vast majority of psychiatric disorders. Second, considerable resources are still being devoted to the search for genes, done using linkage and association models, together with twin and adoption studies, on the basis of case recognition according to conventional disease classification. Recent progress with conventionally specified disorders is reviewed and contrasted with the remarkable advances being made in the identification of the genetic basis of key cognitive processes through the power of modern molecular genetic techniques. Child psychiatric genetic could profit from a new focus on the search for the genetic processes underlying specific cognitive functions that, in turn, underpin child psychiatric disorders, especially those that are neurodevelopmental in origin.