Attention‐deficit hyperactivity disorder (ADHD) is a common disorder of childhood that affects 3–6% of school children. Conventional stimulant medications are recognized as useful symptomatic treatments by both specialists and parents. Nevertheless, approximately 30% of ADHD children treated with them do not respond adequately or cannot tolerate the associated adverse effects. Such difficulties highlight the need for alternative, safe and effective medications in the treatment of this disorder. Theophylline is a psychomotor stimulant most widely used as a broncodilator. Purinergic modulation may be therapeutically beneficial in the treatment of psychiatric disorders. We hypothesized that theophylline would be beneficial for the treatment of ADHD and report results of a trial of theophylline compared with methylphenidate for the treatment of ADHD. A total of 32 children with ADHD as defined by DSM IV were randomized to theophylline and methylphenidate dosed on an age and weight‐adjusted basis at 4 mg/kg/day (under 12 years) and 3 mg/kg/day theophylline (over 12 years) (group 1) and 1 mg/kg/day methylphenidate (group 2) for a 6‐week double‐blind and randomized clinical trial. The principal measure of the outcome was the Teacher and Parent ADHD Rating Scale. Patients were assessed by a child psychiatrist, at baseline and at 14, 28 and 42 days after start of the medication. No significant differences were observed between theophylline and methylphenidate on the Parent and Teacher Rating Scale scores over the trial (t = 0·49, d.f. = 24 P = 0·62 and t = 0·19, d.f. = 24 P = 0·54 respectively). Although the number of dropouts in the methylphenidate group was higher than the theophylline group, there was no significant difference between the two protocols in terms of the dropouts. In addition, headaches were observed more often in the methylphenidate group. The results suggest that theophylline may be a useful for the treatment of ADHD. In addition, a tolerable side‐effect profile is one of the advantages of theophylline in the treatment of ADHD. Nevertheless, our study is small and our results would need to be confirmed in a larger study.