Guided virtual surgery (GVS) has as premise a better accuracy for dental implants placement. However, the reproducibility of the implant planned position by means of surgical guides is still under investigation. This study had as objective to assess the angular and the linear (point of entry and apical extremity) deviations of single-tooth dental implants placed by two different techniques: GVS with stereolithographic guide and conventional surgery (CS) with handmade guide. This split-mouth randomized clinical trial was approved by the Research Ethical Committee involving Human Beings of the Federal University of Santa Catarina (CEPSH - UFSC; Protocol no. 1,658,040/2016) and was registered on the Brazilian Register of Clinical Trials (register number: RBR-2h745w). Twelve patients with bilateral homologous single-tooth missing in posterior mandible were selected (n=24). After scan appliance manufacturing and cone beam computed-tomography (CBCT) by dual scanning technique, cases were virtually planned and forwarded to a prototyping center to stereolitographic surgical guide manufacturing (CAD/CAM). The conventional surgical guides were obtained by scan appliances' preparation. During the surgical procedure, patients were randomized on GVS or CS by a coin toss. Each side of the mandible received one implant by a different technique. After one week, patients underwent a new CBCT scan and the images were superimposed to evaluate the differences of implants positioning between planned and performed. Student's t-test was applied at a significance level of 5% (p=0.05). Angular deviations of GVS implants showed 2.2±1.1 degrees of discrepancy while those placed by CS presented a discrepancy of 3.5±1.6 degrees, and this difference was statistically significant (p-value=0.032). For the variables coronal and apical distances (deviations), however, the null hypothesis was accepted (p-value>0.05), that is, the means between the groups of GVS and CS were not different statistically. It can be concluded that single-tooth implant placement by GVS is more accurate, at least for the angular deviation, when compared to CS with a surgical guide made by hand. Considering the linear deviations (cervical extremity and apical end), the difference between both groups cannot be demonstrated in this study. More randomized clinical trials with larger samples are needed to confirm such trends and to provide solid evidence on the subject. Keywords: dental implants, computer-assisted surgery, oral surgery, cone-beam computed tomography, single-tooth dental implant