Objectives: The aims of this study were to provide a detailed cone beam computed tomography (CBCT) analysis of C-shaped root canals in mandibular second molars from a southern Indian population of Tamil Nadu state and to evaluate their cross-sectional characteristics and periapical radiograph appearances. Materials and methods: In total, 758 patients referred for root canal treatment of mandibular second molar teeth were included in this study. From this, 53 individuals with C-shaped canal anatomy had their 57 teeth subjected to CBCT scans. Differences in prevalence of different types of C-shaped root canal configurations at three different axial levels and their periapical radiograph appearance between genders and ages were compared using chi-squared test. Results: The prevalence of C-shaped canal in mandibular second molars was 7%. Gender difference was significant (P 0.05) with females (38 individuals, 9.1%) having higher incidence compared to males (15 individuals, 4.4%). In 68.4% of teeth the canal configuration changed along the entire length of the root. Radiographic assessment indicated that 43 teeth (75.4%) had a fused root appearance and 14 (24.6%) had two separate roots. Conclusions: The C-shaped canal anatomy presentation varies greatly along the length of the root, which leads to considerable difficulty in debridement and filling of this root canal system. Canal morphology presentation of the population group in this study differs considerably from other studied population groups. Radiographs from one angle will not be adequate to detect the C-shaped canal. CBCT is a clinically effective tool in aiding the understanding of the canal morphology of a C-shaped canal system. Keywords: CBCT, C-shaped canal, mandibular second molar