OBJECTIVES: To assess the clinical and cost-effectiveness of oral methylphenidate hydrochloride (MPH), dexamfetaminesulphate (DEX) and atomoxetine (ATX) in children and adolescents (<18 years of age) diagnosed with attention deficit hyperactivity disorder (ADHD) (including hyperkinetic disorder). DATA SOURCES: Electronic databases covering 1999--July 2004 for MPH, 1997--July 2004 for DEX and 1981--July 2004 for ATX. REVIEW METHODS: Selected studies were assessed using modified criteria based on CRD Report No. 4. Clinical effectiveness data were reported separately for each drug and by the type of comparison. Data for MPH were also analysed separately based on whether it was administered as an immediate release (IR) or extended release (ER) formulation. For all drugs, the data were examined by dose. Data for the core outcomes of hyperactivity (using any scale), Clinical Global Impression [as a proxy of quality of life (QoL)] and adverse events were reported. For crossover studies, the mean and standard deviation (SD) for each outcome were data extracted for end of trial data (i.e. baseline data were not considered). For parallel studies, change scores were reported where given, otherwise means and SDs were presented for end of trial data. In addition, mean differences with 95% confidence intervals were calculated for each study. For adverse events, self-ratings were reported when used, otherwise, parent reports were utilised. Percentages of participants reporting adverse events were used to calculate numbers of events in each treatment arm. All the clinical effectiveness data and economic evaluations (including accompanying models) included in the company submissions were assessed. A new model was developed to assess the cost-effectiveness of the alternative treatments in terms of cost per quality-adjusted life-year. To achieve this, a mixed treatment comparison model was used to estimate the differential mean response rates. Monte Carlo simulation was used to reflect uncertainty in the cost-effectiveness results. RESULTS: In total, 65 papers met the inclusion criteria. The results suggest that MPH and DEX are effective at reducing hyperactivity and improving QoL (as determined by Clinical Global Impression) in children, although the reliability of the MPH study results is not known and there were only a small number of DEX studies. There was consistent evidence that ATX was superior to placebo for hyperactivity and Clinical Global Impression. Studies on ATX more often reported the study methodology well, and the results were likely to be reliable. Very few studies made direct head-to-head comparisons between the drugs or examined a non-drug intervention in combination with MPH, DEX or ATX. Adequate and informative data regarding the potential adverse effects of the drugs were also lacking. The results of the economic evaluation clearly identified an optimal treatment strategy of DEX first-line, followed by IR-MPH for treatment failures, followed by ATX for repeat treatment failures. Where DEX is unsuitable as a first-line therapy, the optimal strategy is IR-MPH first-line, followed by DEX and then ATX. For patients contraindicated to stimulants, ATX is preferred to no treatment. For patients in whom a midday dose of medication is unworkable, ER-MPH is preferred to ATX, and ER-MPH12 appears more cost-effective than ER-MPH8. As identified in the clinical effectiveness review, the reporting of studies was poor, therefore this should be borne in mind when interpreting the model results. CONCLUSIONS: Drug therapy seems to be superior to no drug therapy, no significant differences between the various drugs in terms of efficacy or side effects were found, mainly owing to lack of evidence, and the additional benefits from behavioural therapy (in combination with drug therapy) are uncertain. Given the lack of evidence for any differences in effectiveness between the drugs, the economic model tended to be driven by drug costs, which differed considerably. Future trials examining MPH, DEX and ATX should include the assessment of tolerability and safety as a priority. Longer term follow-up of individuals participating in trials could further inform policy makers and health professionals. Such data could potentially distinguish between these drugs in a clinically useful way. In addition, research examining whether somatic complaints are actually related to drug treatment or to the disorder itself would be informative.