Objective: This study aimed to compare the skeletal and dentoalveolar effects of the expansion force created by the semi-rapid and rapid activation protocols. Material and Methods: The study comprised 54 patients (26 female and 28 male) with transverse maxillary insufficiency. Of these patients, 22 were treated with semi-rapid maxillary expansion (SRME) and 32 with rapid maxillary expansion (RME). The SRME group consisted of 6 prepubertal, 8 pubertal, and 8 postpubertal patients, and the RME group consisted of 11 prepubertal, 11 pubertal, and 10 postpubertal patients. Treatment effects with both protocols were evaluated with 11 different measurements on posteroanterior cephalograms and plaster models taken before treatment and after a retention period of 3 months. Kruskal-Wallis analysis was used for comparisons between different maturation periods. Independent sample t-test and Mann-Whitney U test with Bonferroni correction were used for pairwise comparisons between two different activation protocols. Results: The increases in nasal and dental widths in the SRME group were found to be higher than in the RME group in the prepubertal patient group (p<0.05). There was no significant difference between the SRME and RME groups in pubertal and postpubertal groups (p>0.05). No statistically significant difference was found among prepubertal, pubertal, and postpubertal groups for all skeletal and dental measurements (p>0.05). Conclusion: The current study represented some evidence that the SRME activation protocol might cause less tissue resistance than the conventional RME. The efficiency of maxillary expansion therapy is similar in prepubertal, pubertal, and postpubertal patients in whom sutural resistance is resolved.