The aim of this study was to compare the midterm clinical and radiological outcomes of the Salter osteotomy (SO) and Tonnis lateral acetabuloplasty (TLA) with concomitant open reduction for the treatment of developmental dysplasia of the hip. Twenty-five hips of 20 patients who underwent SO with open reduction and 26 hips of 23 patients who underwent TLA with open reduction were evaluated retrospectively. The average age of the patients at the time of the operation was 35.6 months in the SO and 36.6 months in the TLA group, without a statistically significant difference (P=0.836). The average follow-up times in the SO and TLA groups were 59.9 and 54.8 months, respectively (P=0.397). Preoperative (40.6° in the SO vs. 42.2° in the TLA, P=0.451) and last follow-up acetabular index (12° in the SO vs. 14° in the TLA, P=0.227) and center-edge angle measurements (30° in the SO vs. 26° in the TLA, P=0.069) did not show a statistically significant difference between the SO and TLA groups; however, early postoperative acetabular index improvement was better in the TLA group than in the SO group (21.2° in the SO vs. 17.2° in the TLA, P=0.014). According to the Severin grading system, both groups showed a similar number of good outcomes without a statistically significant difference (P=0.936). Clinical assessment on the basis of McKay’s criteria showed similar good and excellent outcomes (P=0.936). Both osteotomy techniques showed similar satisfactory outcomes for the treatment of DDH in patients older than 18 months of age.