BACKGROUND The aim of this study was to analyze the root canal morphology of maxillary third molars (MTMs) using micro-computed tomography (micro-CT). METHODS Seventy-eight consecutively-extracted human MTMs were scanned using micro-CT (spatial resolution=13.68μm per pixel). Dedicated software (SkyScan®) was used to create virtual reconstructions and perform 3D-analysis. A range of anatomical features were assessed; externally (root number, length, fusion, curvature, apex), within the pulp chamber (distance between canal orifices, floor thickness) and within the root canal system (root canal number, classification, ramifications, isthmuses, apical constriction). RESULTS The donor age ranged from 19 to 73 years (mean±SD 32.3±16.5years). MTMs possessed one or three roots, which principally curved buccally/palatally (75.9%), had 1-4 root canals and typically no apical constriction (84.4%). The average external root length was 11.89±1.53mm, while root canal length was 10.18±0.35mm. The root canal diameter 1mm from the apex was 0.37±0.23mm and negatively correlated with donor's age (r=-0.76; p=0.01), while pulp chamber thickness positively correlated with age (r=0.58; p=0.035). Significantly, furcation canals, canal loops and root canal calcifications were sporadic findings. CONCLUSIONS In some cases the anatomy of MTMs may not be as complicated as previously documented, being similar to the reported anatomy of other maxillary molars. During root canal treatment of MTMs, the frequent deviation of the apical foramen from the radiographic apex should be considered, as should the absence of an apical constriction in the majority of cases. In addition, buccal/palatal root curvature, often undiagnosed radiographically, is the most common root curvature in MTMs.