This study examined social skills and behavior of children with disabilities (CWD) and the impact of siblings on these behaviors. Eighty-five CWD diagnosed with Attention-Deficit Hyperactivity Disorder only (ADHD-o), Learning Disability or Learning Problems (LD/LP), ADHD and LD combined (ADHD/LD) or Spina Bifida (SB) and their siblings were evaluated using standardized social skills and behavior rating scales. The ADHD-o group had significantly lower social skills and more behavior problems than the other groups. There was no recognized effect of the sibling relationship on the social skills and behavioral problems of either the CWD or their siblings. Birth order of the sibling dyads and diagnos(es) of siblings did not have significant influence on the social skills or behavior of CWD. ADHD is a significant risk factor for poor social skills and behavior problems, even when compared with other diagnoses that carry an increased risk of these same problems.