AIM: The aim of this study was to assess the skeletal and dento-alveolar changes produced by a customised eruption guidance appliance (EGA) and a preformed EGA in subjects presenting a skeletal class II pattern during early mixed dentition and to evaluate the differences between the two devices. METHODS: All subjects included in the study were randomly selected from the record's archive according to the following inclusion criteria: (1) patients presenting upper central incisor and first permanent molars fully erupted; (2) early mixed dentition with age between 7 to 9 years old; (3) Angle class I or class II malocclusion; (4) increased overjet > 4 mm;(5) deep bite with at least 2/3 overlapping of the incisors; (6) no previous orthodontic treatment apart from maxillary expansion treatment. All children belonging to the case group received treatment with a 3D printed EGA whereas the other patients belonging to the control group were treated with preformed EGA. Records consisted in digital dental models and lateral cephalogram at the beginning (T0) and after 1 year of treatment (T1). Data collected on the digital models included the dentoalveolar changes in overbite, overjet, sagittal molar relationship, and dental crowding. Cephalometric tracings were computed by a single blinded observer using Dolphin Imaging software. Statistical analysis was performed with SPSS (version 25.00; IBM Corp, Armonk, NY). Comparison regarding the cephalometric changes between T1-T2 was carried out with paired t-test. Difference in distribution regarding sagittal molar and canine relationship and anterior crowding between groups at T1 and T2 has been computed with chi-square test. The independent sample t-test was used to perform the between group comparison. CONCLUSION: In the short time, both the appliances showed to be effective in correcting class II malocclusion, anterior crowding, overjet and overbite. Custom-made appliance demonstrated to be significantly more effective in correcting anterior crowding, the dento-skeletal vertical relation and position of permanent incisor compared to the preformed appliance. Adopting a customised device, effects due to an average prescription appliance used to a specific patient can be reduced, resulting in more predictable results.