Persons with mild and moderate mental retardation and CA-matched persons without mental retardation performed a dual-task, "pencil-and-paper task" (Baddeley, Della Sala, Gray, Papagno, & Spinnler (1997). Testing central executive functioning with a pencil-and-paper test. In Rabbit (Ed.), Methodology of Frontal and Executive Function (pp. 61-80). Hove, East Sussex, UK: Psychology Press), which includes a memory span task and a tracking task. The memory span task loads onto phonological working memory and the tracking task loads onto visuo-spatial working memory. By comparing performance between single and dual-task, we assessed the characteristics of executive function, which allocates attentional resources between two tasks. Results indicate that there was no difference in the characteristics between the two groups, and there was no improvement in the characteristics with practice. Thus, we suggest that when persons with mental retardation perform a dual-task that have no interference in the sub-storage of working memory, their function of attentional allocation can work without impairment.