One of the most contentious ethical issues in the neonatal intensive care unit is the withdrawal of life-sustaining treatment from infants who may otherwise survive. In practice, one of the most important factors influencing this decision is the prediction that the infant will be severely intellectually disabled. Most professional guidelines suggest that decisions should be made on the basis of the best interests of the infant. It is, however, not clear how intellectual disability affects those interests. Why should intellectual disability be more important than physical disability to the future interests of an infant? Is it discriminatory to base decisions on this? This paper will try to unravel the above questions. It seems that if intellectual disability does affect the best interests of the child it must do so in one of three ways. These possibilities will be discussed as well as the major challenges to the notion that intellectual disability should have a role in such decisions. The best interests of the child can be affected by severe or profound intellectual disability. It is, though, not as clear-cut as some might expect.