Objective There are a few studies regarding the prevalence of testicular adrenal rest tumours (TARTs) in boys and adolescent males with congenital adrenal hyperplasia (CAH), and there is little information regarding the treatment outcomes in patients with TARTs. The aim of this study was to determine the long-term treatment outcomes in boys and adolescent males with CAH. Patients and methods Sixty boys and adolescent males with CAH, who were between 2 and 18years of age, were included in the study. Fifty-five patients had 21-hydroxylase deficiency (21-OHD), and five patients had 11- hydroxylase deficiency (11-OHD). All patients were screened for TARTs by scrotal ultrasonography (US) performed by an experienced radiologist. Results TART prevalence was 18 center dot 3% in 218years' of age; eight patients had 21-OHD, and three had 11-OHD. The youngest patient with TART was 4years old, whereas eight patients with RTs were at puberty. Only two patients had tight metabolic control: eight patients had stage 2, one had stage 4, and two had stage five rest tumours. In four patients with stage 2 TARTs, tumours disappeared after high-dose steroid treatment and did not recur. Shrinkage of tumour was observed in two patients. Testis-sparing surgery was performed in one patient with stage five tumour. Gonadal functions were normal in patients with partially regressed tumours. Two patients became fathers of healthy male off-springs. Conclusions Detection and treatment for TARTs in children with CAH at younger ages, earlier stages, may prevent infertility in adulthood. Therefore, we recommend that scrotal US screening should be performed in every 12years starting from early childhood.