Systematically review and analyse the efficacy of CBT versus treatment as usual in adults with ADHD. The literature was systematically searched ending the 28 March 2014. Standardised mean differences (SMD) and 95% confidence intervals were calculated. CBT was efficacious in reducing symptoms of ADHD (SDM -1.0, 95% CI -1.5 to -0.5) when evaluated by the patients, but not when evaluated by a clinician. Symptoms of depression and anxiety were significantly reduced when self-reported (SMD -1.0, 95% CI -1.6 to -0.5 and -1.0, 95% CI -1.3 to -0.3, respectively) and evaluated by a clinician (SMD -0.9, 95% CI -1.7 to -0.2 and -0.9, 95% CI -1.6 to -0.1). The clinical global impression scores improved more in the group randomised to CBT (-1.0; 95% CI -1.6 to -0.4). CBT seems efficacious in some domains affecting adult patients with ADHD, but needs further evaluation.