Introduction: In this study, we compared the effects of functional treatment with Twin-block appliance on the bony architectures of the maxilla and mandible by fractal dimension (FD) analysis, and the skeletal and dentoalveolar effects by cephalometric analysis, in pubertal and postpubertal patients with Class II malocclusion. Methods: This study comprised 60 patients who underwent Twin-block treatment. Group 1 consisted of 30 patients in the pubertal period (6 boys and 24 girls; mean age 12.27 +/- 1.35 years), whereas group 2 consisted of 30 patients in the postpubertal period (6 boys and 24 girls; mean age 13.73 +/- 1.51 years). FD analysis was performed on the patients before and after Twin-block panoramic and lateral cephalometric radiographs. Cephalometric analysis was also conducted. Paired and Student t tests were used to compare the parametric data, and Wilcoxon signed rank and Mann-Whitney U tests were conducted to compare the nonparametric data. Results: SNB, Pg-N, N-Me, ANS-Me, IMPA, L1/NB, Co-Gn, Go-Gn, S -Go, Co-Go, and Go-Me significantly increased in both groups after treatment. FD values of tuber, condyle, and molar regions significantly decreased in group 1, whereas no significant differences were observed in group 2 after treatment. Conclusions: In the pubertal period, the Twin-block appliance resulted in skeletal correction by causing bone remodeling and reshaping in both jaws along with the dentoalveolar correction. In the postpubertal period, Twin-block had no significant effect on the bone trabecular arrangement in the investigated areas but produced cephalometric improvement to a certain extent with lower skeletal and higher dental impact.