The aim of this study was to evaluate both the precision of filling and the extension of voids in main root canals as well as filling of lateral canals after using a two-phase filling technique with two sealers. Twenty-four maxillary and 26 mandibular molars were selected and randomly assigned to two groups. Root canals were instrumented and then filled using the vertical compaction with the apical backfilling technique, with Pulp Canal Sealer (EWT) in group "A" and AH Plus in group "B." After clearing, voids within the filled main canals were measured by using a stereomicroscope. In addition, visible lateral canals were counted, each unfilled space was measured, and five ratings (0-4) were fixed. In both groups, in the most apical 4 mm of main canals, where gutta-percha was cold compacted, lesser voids (p <or= 0.05) were found than in the middle-coronal thirds backfilled with thermomechanical compaction. In group "B," more precision (p <or= 0.05) and lesser voids (p <or= 0.05) were found than in group "A." Regarding lateral canals, better filling scores (p <or= 0.05) were found in group "B" than in group "A." In both groups, better filling scores (p <or= 0.05) were found at the coronal levels than at the middle ones and at the middle levels than at the apical ones.