Objective:To identify the etiologic factors associated with palatally impacted canines and buccally impacted canines in a Chinese population using the cone-beam computed tomography (CBCT) technique. Methods:CBCT images of 262 Chinese subjects with impacted maxillary canines(buccally impacted canines and palatally impacted canines) and 262 age- and sex-matched subjects without impaction were admitted to the study. All CBCT records were analyzed in software programs for quatitative and quantitative variables of the teeth,dental arch and skeletal components by one rater. The differences among groups were compared statistically (SPSS 13.0 software). Results:The mesiodistal dimension of the lateral incisor was significantly smaller in the palatally impacted canine group than that in the other groups(P < 0.001). Both anterior maxillary dental width and skeletal width in the buccally impacted canine group were significantly smaller than those in the control group (P < 0.001). The groups with palatally impacted and buccally impacted canines had significantly increased prevalence of peg-shaped lateral incisors and incisor impaction,respectively(P < 0.001). The average mesiodistal location of the canine cusp tip was significantly different between the buccally impacted canines and the palatally impacted canines groups,being mesial and distal to the lateral incisor long axis,respectively. Conclusion:In Chinese subjects,buccal canine impaction is mostly associated with anterior transverse(dental and skeletal) deficiency and incisor impaction,however,palatal impaction is mostly associated with small or missing lateral incisors,consistent with the guidance theory. A mechanism is proposed to explain the processes leading to different fates of canine eruption in response to varied local factors.