The present study aims to gain insight into the clinical presentation (viz., self-reported complaints and neuropsychological functioning) of adults referred for an attention-deficit hyperactivity disorder (ADHD) diagnosis. The investigation evaluated group differences between an ADHD and a non-ADHD sample (n = 30 and n = 42, respectively), all of which had been clinically referred for multidisciplinary assessment of ADHD. Forty-two percent of all referred patients were diagnosed with adult ADHD. Adults with ADHD made significantly more errors on a verbal learning task than the non-ADHD control group, which could indicate an impairment of the self-monitoring function in adult ADHD. The ADHD group reported more problems than the control group in the domains of executive functioning but not in the domains of attention and hyperactivity. More attention should be paid to executive complaints and functioning (present and past) when referring adults suspected of ADHD for multidisciplinary assessment. Also, characteristics that are thought to be striking symptoms of adult ADHD, such as problems with concentration and hyperactive behavior, are in fact not distinctive symptoms of ADHD at all.