The project Adult Dyslexia and Attention Deficit Disorder in Finland (Project DyAdd) compares adults (n = 119, 18-55 years) with dyslexia, attention-deficit/hyperactivity disorder (ADHD), dyslexia together with ADHD (comorbid), and healthy controls with neuropsychological, psychophysical, and biological methods. The focus of this article is on the Wechsler Adult Intelligence Scale-Third Edition (WAIS-III). The clinical groups performed well compared to the norms, and they did not differ from each other. However, compared to the controls, all of them were slightly poorer in their Full IQ, and of the factors, processing speed was relatively difficult for all of them. In addition to the group comparisons, a cluster analysis based on subtest scores was conducted over the clinical groups. It did not suggest a solution that would differentiate between the clinical groups. Instead, four clusters emerged: above average, average, poor perceptual organization, and poor working memory. Thus, differentiating between these clinical groups with the WAIS-III was not possible. However, all of them shared a relative difficulty in processing speed, and group-independent clusters with perceptual or memory difficulties emerged.