The aim of the present study was to evaluate and compare the effects of single- and two-dose low-level laser therapy (LLLT) on the postoperative swelling, trismus and pain of patients undergoing extraction of impacted mandibular third molars. In addition, edema was volumetrically measured with a 3dMD face system. A total of 45 patients were randomly divided into three treatment groups (15 patients in each group) as follows: Group 1, receiving routine management with ice application and serving as the control group; Group 2, receiving a single dose of LLLT immediately following surgery; and Group 3, receiving two doses of LLLT, immediately following surgery and on day 2 after surgery. In the present study, a gallium-aluminum-arsenide (0.3 W, 40 sec, 4 J/cm(2)) diode laser device was applied extraorally at the insertion point of the masseter muscle. The trismus, pain level and facial swelling of the patients were evaluated. The visual analog scale (VAS) was used to examine the pain degree, while a 3dMD face photogrammetric system was used to evaluate the volumetric alterations of the swelling. The results indicated no statistically significant differences in the mean swelling or trismus among the three groups. The mean VAS measurements did not differ significantly among the groups at postoperative day 2; however, significantly reduced VAS values were observed in Group 2 compared with Group 1 at postoperative day 7 (P<0.05). The present study demonstrated that, although single-dose or two-dose LLLT had beneficial effects on the swelling, trismus and pain level, a significant reduction was only observed in the pain level at postoperative day 7.