A proportion of children within the autism spectrum is at risk for severe deregulation of thought, emotion and behaviour resulting in (symptoms of) psychotic disorders over the course of development. In an attempt to identify this subgroup, children with PDD-NOS, subtype MCDD (n = 24) were compared to children with PDD-NOS (n = 23) on executive function (EF) skills. Significant differences emerged, always to the disadvantage of the children with PDD-NOS, subtype MCDD on various EF measures. The findings suggest compromised attention regulation and impaired inhibitory control in children with MCDD, which may help explain high levels of thought problems which are frequently observed in these children. Our findings provide evidence for recognizing a PDD subcategory of MCDD that is of specific interest with regard to long-term developmental risks involved.