The aim of this in vitro study was to compare the efficacies of two different fiber post-removal systems. Thirty extracted single-rooted mandibular premolar teeth were used. After RelyX fiber posts were cemented, the teeth were divided into two groups with regard to the post removal techniques: ultrasonic vibration and D.T. Light-Post removal kit. Residual material, tooth volume changes, working time and micro-crack formation were assessed using micro-computed tomography. All data were analyzed using Wilcoxon signed-rank and Mann-Whitney U tests. There was significantly more tooth root volume change in the ultrasonic group than removal kit group (p < .05). Fiber post removal time for the ultrasonic group was significantly longer than the removal kit group (p < .01).