© 2021 Ayse I. Orhan and Esra C. Tatli.Objective. To evaluate the voids in root canal treatment of deciduous molar canals using three obturating materials and two obturation systems using micro-CT. Study Design. Thirty freshly extracted deciduous molars were used in this study. The specimens were instrumented using a ProTaper Universal rotary instrument and randomly assigned into six groups (n=5). Mesiobuccal root canals were obturated using Ca(OH)2 and iodoform-Ca(OH)2 and ZOE cement. The materials were applied straight from the syringe up to the 2 mm coronal level of the apex. Subsequently, the Lentulo spiral and ultrasonic activation with endoactivator were used for obturation. All samples were scanned by micro-CT with 9.1 μm isotropic voxel resolution. The voids in cross-sectional images and 3D volumes of voids were measured. Differences among materials were statically evaluated (p<0.05). Results. All study groups showed voids. Ca(OH)2 and iodoform-Ca(OH)2 with ultrasonic activation produced fewer voids whereas the ZOE groups showed higher voids with statistical significance (p<0.05). Conclusions. Ca(OH)2 and iodoform-Ca(OH)2 with ultrasonic activation decrease void formation. Further studies should be done with other obturation techniques and materials for deciduous tooth root canal management.