The performance of 25 children with Down syndrome on delay of gratification tasks was compared with that of a mental age-matched group of typically developing children. Delay tasks included both other- and self-imposed tasks. Children with Down syndrome were significantly less able to delay gratification than the comparison group on two of the three tasks. Receptive language was associated with delay on the self-imposed task for the typically developing group but not for children with Down syndrome. It is hypothesised that there may be a lag in the development of self-regulation that is greater than the lag between chronological and mental age for children with Down syndrome, with expressive language playing a role in this lag. The practice of using mental age as the method for matching groups of children with Down syndrome with typically developing children is called into question by the results of this study.