The Integrated Visual and Auditory (IVA) Continuous Performance Test (CPT) and Neuropsychological Impairment Scale (NIS) were completed by adults diagnosed with mild traumatic brain injury (mTBI), adults diagnosed with attention deficit hyperactivity disorder (ADHD), and controls. On the IVA CPT, the mTBI and ADHD groups performed significantly lower on the full and secondary scales for attention and response accuracy. For individual scales, the mTBI and ADHD groups showed lower performance on measures of reaction time, inattention, impulsivity, and variability of RT. The mTBI and ADHD groups showed similar patterns of performance on the IVA. On the NIS, the mTBI and ADHD groups reported more neuropsychological symptoms than the control group, and the mTBI group reported more neuropsychological symptoms than the ADHD group. The results are discussed in regard to changes in cognitive processing and sustained attention in individuals diagnosed with mTBI and ADHD.