The purpose of the study is to explore the effect of methylphenidate on state anxiety in children with attention deficit hyperactivity disorder.

Patient population: 30 children diagnosed with attention deficit hyperactivity disorder. The subjects will be of all racial, ethnical and gender categories, ranging from 8 to 18 years of age.

Structure: the study is a randomized double blind crossover study. The subjects will complete a continuous performance test, the cambridge neuropsychological test automated Battery, before and after given methylphenidate or placebo on the first day of the study. On the second day of the study, the subjects will receive either methylphenidate or placebo based on what was given on the first day of the study and they will complete the same task.

Inclusion Criteria:

• Attention deficit and hyperactivity disorder
• Children aged 8-18 years

Exclusion Criteria:

• Pervasive developmental disorder
• Schizophrenia
• Bipolar disorder
• Current depressive episode
• Current Anxiety disorder
• Drug use during the past 6 months