A large body of research documents underlying cognitive factors, many of which are shared, in students with reading disabilities (RDs), math disabilities (MDs), comorbid reading and math disabilities (RD + MD), as well as students with attention deficit/hyperactivity disorder (ADHD) and students with RD and ADHD. In an effort to examine differences in reading, mathematics, and cognitive outcomes among these students, we investigated the outcomes between these groups across the published research literature by conducting a systematic review. A total of 16 studies met inclusion criteria. Data from a total of 1,910 participants across studies was used to answer our research questions. Mean effect size differences across studies highlight lower overall outcomes for students with RD + MD and students with RD + ADHD compared to students with RD, MD, or ADHD alone.