Aim: This study tests whether rapid maxillary expansion (RME) exerts long term effects on interglenoid fossa distance and condyle fossa relationship. Materials and methods: Consecutive growing patients aged 8 to 13 years were allocated either to the RME group or control group. Cone-beam computed tomography was performed at baseline and at 6 months. Specific software was used to determine fixed landmarks. Multivariate Analysis of Covariance (MANCOVA) models were used, with time by group interaction, using age as a covariate. Results: Twenty-seven patients with a mean age of 11.4 ± 1.5 years were included. There was an overall significant group by time interaction (p = 0.012, effect size 0.59). Change in the lateral position of the glenoid fossa, the primary outcome, was reached (p = 0.008, effect size 0.258). Change in the laterolateral position of the center of the condyle, and the co-primary outcome was also significant (p = 0.011, effect size = 0.24). Nasal cavity width increased (p = 0.065, effect s ize = 0.14). There was aninitial a symmetry in the horizontal position of the condyles that was carried on with no effect of RME. Conclusion: Rapid maxillary expansion (RME) produces a significant increase in the interglenoid fossa distance and displacement of the mandibular condyles at 6 months in growing patients compared to a control group. Clinical significance: The current study shows that RME is effective during growth, widening the interglenoid fossa distance and the lateral positions of the condyles and eventually enlarging the nasal cavity, without causing asymmetry.