The aim of this study was to determine the area filled by gutta-percha and sealer and occupied by voids in the different thirds of root canals shaped with ProTaper and sealed using two different single-cone techniques. The root canals of 20 mandibular premolars were prepared with Gates Glidden drills #1, 2 and 3, and shaped using ProTaper instruments. The teeth were randomly divided into two groups; in group G1 the canals were obturated with a single ProTaper F3 cone, and in group G2 with a single 0.06 taper size 40 gutta-percha cone, using N-Rickert sealer in both groups. The roots were sectioned transversally into thirds, and the quantities of gutta-percha and sealer were assessed by ANOVA and post-hoc Tukey test. The voids were analysed by the Kruskal-Wallis test, with a comparison of ranked means by the Student-Newman-Keuls test. In all cases, the level of significance was set at 5%. The amounts of gutta-percha and sealer showed significant differences between the techniques in the different root thirds (P 0.0001). Group G1 showed less gutta-percha when compared to group G2, and there was a greater quantity of sealer in the cervical third with both techniques. In relation to the percentage of voids, the middle third of group G1 differed from the middle and apical thirds of group G2 (P 0.05). The use of 0.06 taper gutta-percha cones in root canals shaped with ProTaper resulted in more satisfactory results when compared to the original ProTaper single-cone technique. Keywords: gutta-percha, ProTaper, root canal obturation, voids