Aim: The aim of the present study was to compare the canal transportation and centering ability of Rotary I-Race and BT-Race systems using cone beam computed tomography (CBCT) in curved root canals (40°) to find better instrumentation technique for maintaining root canal geometry. Materials and methods: Thirty endodontic training blocks, with angle of curvature 40°, were selected into two groups of 15 samples each: BT-Race (group I), I-Race (group II). The blocks were placed in mold made by silicon impression material to facilitate instrumentation and to enable the reproducibility of pre-and postoperative CBCT images. Preinstrumentation and postinstrumentation images were obtained at three levels, 1, 3, and 5 mm above the apical foramen and were compared using CBCT software. Amount of transportation and centering ability were assessed. The two groups were statistically compared with one-way analysis of variance (ANOVA). Results: The mean transportation for group I at 1, 3, and 5 mm apical was 0.160, 0.080, and 0.046 mm respectively. The mean transportation for group II at 1, 3, and 5 mm apical was −0.096, 0.050, and −0.080 mm respectively. The mean centering ratio for group I at 1, 3, and 5 mm apical was 0.401, 0.481, and 0.533 mm respectively. The mean centering ratio for group II at 1, 3, and 5 mm apical was 0.428, 0.540, and 0.598 mm respectively. Conclusion: Under the condition of this study, the two groups showed significant difference and it was found that BT-Race files (group I) have better centering ability and less canal transportation than I-Race (group II). Clinical significance: The CBCT study will be a more accurate way of estimation of centering ability and canal transportation and hence, will reduce the clinical complications while performing biomechanical preparations. © 2018, Jaypee Brothers Medical Publishers (P) Ltd. All rights reserved.