Hyperadrenocorticism caused by tumors of adrenal cortex is uncommon in children; it occurs more frequently in girls and on the left side. The clinical manifestations depend upon age and sex of patients; virilization is the predominant sign in about two thirds of the cases, and Cushing's syndrome in the others. Diagnosis is made by hormonal and instrumental evaluations. Therapy is surgical eradication. Histology has not proved to be useful because pleiomorphism and capsular invasion have been found in clinically benign tumors. High mortality rate in older literature may have been due to post-operative complications and inadequate steroid replacement; in more recent issues good prognosis is referred in pediatric patients. Early diagnosis and therapy are important to prevent adverse effect on growth and development. After an up-to-date review of the literature, a case of adrenocortical tumor is reported. We present a 3 years old boy with pseudoprecocious puberty (accelerated growth and bone age, sexual hair, facial acne, penile enlargement, hoarse voice) and a diagnosis of testosterone-producing adrenal tumor was confirmed by endocrine and radiological investigations. Removal of functioning adrenal tumor was followed by rapid regression of most of the clinical signs of the disease; plasma and urinary steroids returned to normal values. Twelve months after eradication of the tumor the patient is in good health; long-term-follow-up is necessary to exclude any relapse.