Introduction: Lack of knowledge about root canal anatomy can cause mistakes in diagnosis, treatment planning and failure of treatment. Mandibular canine is usually single-rooted it may have two roots or more root canals. The purpose of this study was evaluating the number of root and root-canals of mandibular canine using digital radiography with different angles and comparing it with clearing method.Materials & Methods: This study was a diagnostic test. Two hundred human mandibular canine teeth were studied. Digital radiography of the teeth from mesiodistal, bacculingual and 200 mesial views were prepared. Radiographic evaluation was down by two observers (An oral radiologist and an endodontist) separately. Then dental clearing was performed. Data analysis was done using SPSS.Ver.17 software and statistical tests of MC Nemar. P<0.05 was considered significant.Results: Out of 200 cases of mandibular canine teeth, six teeth had two roots. In clearing method 183 teeth (91.5%) had single-canal and 17 cases (8.5 %) had two canals, and 3 teeth were type II and 8 teeth were type III. Digital x-ray results in bacculingual view showed that 198 teeth (99%) were single-canal and 2 cases (1%) were two-canal, which showed a significant difference compared to the results of clearing method (P>0.001). Findings of digital radiography in mesiodistal view showed that 180 teeth (90%) were single-canal and 20 teeth (10%) had two canals, which were not different from those of clearing method (P=0.25). In 200 mesial view, 192 teeth (96%) were single-canal and 8 teeth (4%) had two canals, which were different from those of clearing method (P=0.012).Conclusion: Despite the low prevalence of anatomical variations in mandibular canine in this in vitro study, due to the lack of significant difference of radiographic mesiodistal views compared to that of clearing technique, CBCT modality is recommended for obtaining fast and complete diagnosis of unusual root canal.