Children with autistic disorder (AD), mixed receptive-expressive language disorder (RELD), or developmental coordination disorder (DCD) have impairments in common. We assess which abilities differentiate the disorders. Children aged 3-13 years diagnosed with AD (n = 30), RELD (n = 30), or DCD (n = 22) were tested on measures of language, intelligence, social cognition, motor coordination, and executive functioning. Results indicate that the AD and DCD groups have poorer fine and gross motor coordination and better response inhibition than the RELD group. The AD and DCD groups differ in fine and gross motor coordination, emotion understanding, and theory of mind scores (AD always lower), but discriminant function analysis yielded a non-significant function and more classification errors for these groups. In terms of ability scores, the AD and DCD groups appear to differ more in severity than in kind.