OBJECTIVE To determine the prevalence of and risk factors for decreased bone mineral density (BMD) and vitamin D deficiency in children and adolescents with congenital adrenal hyperplasia (CAH). METHODS This study was conducted on 30 girls and 22 boys with CAH (age range = 5-20 years) with median age of 12.0 years. BMD values of lumbar vertebras (L1-L4), which were determined by dual-energy X-ray absorptiometry, were used to calculate z-scores according to chronological age. A serum 25-hydroxyvitamin D level of <15 ng/mL was considered as indicative of vitamin D deficiency. RESULTS Mean vitamin D level was 14.8 ng/mL in the whole group. Twenty-seven (51.9%) children had vitamin D deficiency and it was more prevalent during pubertal ages. Vitamin D levels were found to be significantly lower in pubertal females. BMD z-score was below -1 standard deviation in 40.1% of cases with significantly higher mean age and lower vitamin D levels. CONCLUSIONS Decreased BMD z-score and vitamin D deficiency were common in these children with CAH. Vitamin D levels were significantly lower in girls and pubertal children. Decreased BMD z-score was related to older age and lower levels of vitamin D. Periodical controls of vitamin D status and vitamin D supplementation were recommended in these cases, whenever required.