As a result of the widespread use and enhanced quality of high-resolution radiological techniques, a recent report has revealed a relatively high prevalence of small adrenal tumors in patients with untreated congenital adrenal hyperplasia due to 21-hydroxylase deficiency. However, there are scarcely any pediatric cases of adrenocortical tumor following long-term treatment in patients suffering with congenital adrenal hyperplasia. We report here on a pediatric female case of adrenocortical adenoma despite adequate long-term treatment for the salt-losing type of congenital adrenal hyperplasia.