The use of traditional intra-oral devices in maxillary molar distalization is not without undesirable consequences. The aim of the present study was to compare the miniscrew-supported distal-jet appliance to a traditional distal-jet appliance by evaluating the amount of upper first molar distalization and the dentoalveolar side effects. Data of 600 subjects visited at the orthodontic unit of Sapienza University of Rom were analyzed. Only 46 patients met the inclusion criteria and were selected and treated. Subjects were assigned randomly to receive treatment either with miniscrew-supported distal-jet appliance (Group A) or with a traditional distal-jet appliance (Group B). In Group A, miniscrews were inserted using a computer-guided surgical guide. The amount of upper first molar distalization and the dentoalveolar side effects were assessed both on the digital casts and on the lateral cephalometric radiograph at the end of the distalization phase. A descriptive statistical analysis that included the mean values and the standard deviation was conducted to evaluate the molar distalization and the dentoalveolar effects in two groups. Intergroup differences were determined using the Student's -test. The significance was set at ≤ 0.05. In Group A, greater maxillary first molar distalization and a spontaneous distalization of the first premolars and a palatal inclination of central incisors were observed. By contrast, in Group B, the first premolars tipped mesially and a proclination of the maxillary central incisors was observed. In both groups, the transverse widths of the dental arch increased while a greater tendency of first premolar extrusion and of maxillary first molar rotation was observed in Group B. The skeletal anchorage device achieved greater first molar distalization and did not cause dento-alveolar side effects.