Abstract: Objective To determine the value of low dose spiral CT scanning in diagnosing impacted teeth of children and adolescents. Methods A total of 153 children and adolescents with confirmed impacted teeth in West China Second University Hospital, Sichuan University were enrolled in this study. They were divided into 5 groups according to the different spiral CT scan parameters (tube current time product, scanning thickness and collimation value): Group A (n=30, 330 mAs, 6×0.75 mm and 3.0 mm), Group B (n=30, 140 mAs, 6×0.75 mm and 3.0 mm), Group C (n=30, 80 mAs, 6×0.75 mm and 3.0 mm), Group D (n=31, 80 mAs, 6×1.50 mm and 5.0 mm), and Group E (n=32, 50 mAs, 6×1.50 mm and 5.0 mm). There were no significant differences in general clinical features ( P>0.05) among the participants of the five groups. The phantoms were used to measure spatial resolution and contrast resolution of the scan images. Dose length product (DLP) was recorded during CT scanning for calculating effective dose (ED) of exposure. The quality of images was evaluated using a list of quality scoring criteria. Results ① Under 330, 140, 80, 80 and 50 mAs, the images had a spatial resolution of 1.0 mm, with contrast resolution of 2.0, 3.0, 4.5, 4.5 and 6.0 mm, respectively. ② Significant differences in ED values were found among the five groups (F=1 064.119, P=0.000) and between every two of those groups ( P<0.05). Group E had the lowest ED (0.19 mSv), 86.52％, 67.24％, 45.71％, and 38.71％ lower than that in Group A, B, C and D, respectively ( P<0.05). ③ All of the five groups obtained an image quality score above 3, and no statistical differences appeared among the 5 groups （F=1.978, P>0.05）. The diagnostic results of the spiral CT were consistent with those of orthodontic surgery. Conclusion Low dose spiral CT scanning can meet the image quality requirements for diagnosing impacted teeth, minimizing radiation exposure effectively.