Objective ·To explore the characteristics of mandibular deviation (MD) in adolescent patients with anterior disc displacement (ADD) and the relationship between temporomandibular joint (TMJ) anterior disc displacement and mandibular deviation. Methods ·Consecutive cases aged 12 to 15 who has been treated in the Department of Oral Surgery of Shanghai Ninth People's Hospital from January 2019 to December 2019 were reviewed. Among them, cases with TMJ symptoms, having been diagnosed by MRI as unilateral or bilateral TMJ ADD, were separately included into unilateral displacement group and bilateral displacement group. Cases without TMJ symptoms, showing a normal disc-condyle relationship with MRI, were included into the control group. The posteroanterior cephalometric radiographs of the three groups were collected respectively before orthodontic treatment, which were measured independently by two surveyors. SPSS 23.0 software package was used for statistical processing, and Shapiro-Wilk was used to test its normality. Pearson chi-square test was used to analyze the distribution of mandibular deviation in the three groups, and the degrees of horizontal deviation of submental point in the three groups were compared. The distribution characteristics of mandibular deviation in cases with disc displacement were observed by comparing the mandibular deviation between juvenile patients with TMJ anterior disc displacement and those with normal disc-condyle relationship. Results ·A total of 1 011 cases of 12-15-year-old adolescent patients in our hospital were collected, including 192 cases of unilateral disc displacement group and 255 cases of bilateral disc displacement group. A total of 564 cases were collected in the control group. Both the control group and the disc displacement group showed a skewed distribution. The mean value of Me_H in the control group was 2.1 mm. While 3.6 mm was taken as the critical value to distinguish deviation and non-deviation, the proportion of patients with mandibular deviation in the control group, unilateral displacement group and bilateral displacement group was respectively 25.53%, 27.08% and 19.22%. The incidence rate of mandibular deviation was significantly different between the unilateral displacement group and bilateral displacement group (P=0.049). Among all cases with mandible deviation, 68.16% (167/245) were mild deviation (3.6 mm≤Me_H<5.8 mm), 21.22% (52/245) were moderate deviation (5.8 mm≤Me_H<8.2 mm), and 10.61% (26/245) were severe deviation (Me_H≥8.2 mm). Conclusion ·It is found that about 75% of adolescents have mandibular deviation within 3.6 mm; Patients with unilateral anterior disc displacement have a greater probability of deviation than the general population.