This study examined the influences of intention on continuous bimanual circle drawing performed by adults with Down syndrome (DS) and mental age (MA) and chronological age (CA) matched comparison groups. The task was performed with preferred and instructed coordination patterns paced by a 500 ms metronome. While all participants adopted an in-phase coordination mode in the preferred conditions, only the adults with DS were unable to perform in-phase coordination when instructed to do so. We suggest that intention to perform specific coordination patterns taxes the attentional resources available, and mental age may be a precipitating factor to appropriate attention directing when performing multiple tasks. Results are discussed with respect to the developmental differences in attentional resources.