Wolf-Hirschhorn syndrome (WHS) is a rare genetic disorder. To determine the nature and variability of mental retardation and a possible peculiar neuropsychological phenotype, a psychometric assessment on 57 individuals, 2.6-28.6 years of age, with Wolf-Hirschhorn syndrome was conducted. This sample represents 70% of Italian known WHS population. Results obtained, through administration of Griffiths Scale for Assessment of Mental Development, show a peculiar Neuropsychological Phenotype for WHS consistently characterized by variably degrees of mental retardation. Neuropsychological Phenotype with mild impairment seems to be associate with mild clinical signs: This finding supports recent hypotheses reported in the literature of a possible mild form of WHS. Delineating a specific WHS Neuropsychological Phenotype is necessary to design an effective rehabilitation treatment aimed at this pathology.