The relation between obesity and age in children with idiopathic intracranial hypertension (pseudotumor cerebri) has remained uncertain. The authors reviewed the records of 45 consecutive children with newly diagnosed idiopathic intracranial hypertension seen at two medical centers. Forty-three percent of patients aged 3 to 11 years were obese, whereas 81% of those in the 12- to 14-year age group and 91% of those in the 15- to 17-year age group met criteria for obesity (p = 0.01). Younger children with idiopathic intracranial hypertension are less likely to be obese than are older children or adults.