A 12-year-old female with severe root resorption in the maxillary left central and lateral incisors (Case 1) and a 27-years-old female with the maxillary left canine erupted in the position of the central incisor (Case 2) were examined and treated. The findings and treatment procedures were as follows: 1. In Case 1, severe root resorption was caused by the ectopic eruption of the canine. On the lingual surface, the resorption had proceeded to a part of enamel. 2. In the Case 1, after the central and lateral incisors were extracted, the canine was carefully guided into the position of the lateral incisor. 3. In Case 2, treatment was not performed, because the chief compliant was carious lesions and the patient did not mind the malposition of the canine. 4. In both Case 1 and 2, the main reason of ectopic eruption of canines was presumably not a discrepancy between the tooth material and the basal arch length but the malposition of the tooth germ and/or abnormal eruption process of the canine.