A 3-way cross-over trial of two weeks of treatment with three drug conditions. AZD3480 will be given in doses of (A) 5mg/day, (B) 50 mg/day and (C) placebo to 24 non-smoking adults with DSM-IV confirmed ADHD. Three week washout between each treatment period. CYP2D6 genotyping will be completed at screening and slow metabolisers will be excluded from participation in this study. Cognitive, ADHD symptom, safety and pharmacokinetic (PK) assessments will be made during each treatment period. Safety and tolerability assessments will be a major component of the trial and all serious adverse events (SAE) will be immediately (within 24 hours) reported to both Targacept and to AstraZenca.