Parents (N = 19) of children with autism spectrum disorders (ASD) and adult controls (N = 17) underwent positron emission tomography (PET) using [(18)F]setoperone to image cortical serotonin type-2 (5-HT2) receptors. The 5-HT2 binding potentials (BPs) were calculated by ratioing [(18)F]setoperone intensity in regions of interest (ROI) to cerebellar intensity. Cortical 5-HT2 BPs were significantly lower in parents compared to controls and platelet 5-HT levels were significantly negatively correlated with cortical 5-HT2 BP in parents. Lower cortical 5-HT2 receptor density in parents of children with ASD is consistent with reports of diminished 5-HT2 expression and functioning in individuals with ASD. Further research should examine the relationship of reduced 5-HT2 receptor expression to underlying causation and to clinical and neurochemical correlates of autistic behavior.