Accurate age determination is important in paediatric dentistry, orthodontics, forensic identification of deceased persons, among other reasons. In developing countries where accurate birth records are lacking, scientific methods of accurately assessing patients' ages are relevant. Many methods for age determination using the dentition exist but the most widely used is that proposed by Demirjian in 1973. This study aimed to determine the accuracy of age determination using the Demirjian method among Nigerian children.Orthopanthomograms of children seen at the orthodontic clinic of the University College Hospital, Ibadan were reviewed. Chronological age was calculated from date of birth recorded at registration to the nearest decimal. Dental age was calculated using the Demirjian criteria (1973). Boys and girls were analysed separately to allow for gender related variations in dental development. The paired t-test and correlation analysis were used to compare the chronological age and calculated dental age.Ninety-three children (41 boys and 52 girls) with ages ranging from 4.42 to 16.75 years (mean 10.69 years for boys and 10.50 years for girls) were assessed using the Demirjian method. There was a significant difference between the chronological and dental age among the boys (p = 0.009); the converse was the case among the girls (p = 0.051). The chronological and dental age of the children showed high correlation (p < 0.01).There are variations between chronological age and dental development among Nigerian children. Other methods of age determination should be explored for this population.