Introduction: The hypothesis behind this study is that the ectopic mandibular canines move vertically in the mandibular bone during childhood and puberty. The aim was to evaluate interosseous vertical movements of the ectopic mandibular canines for improvement of diagnostic treatment and planning. Material and Methods: The study had two parts: a cross-sectional study and a longitudinal study. The cross-sectional study included orthopantomograms from 54 patients (ages 9 years and 6 months to 16 years) with ectopic mandibular canines. The longitudinal study included series of orthopantomograms from 14 out of the 54 patients. Two methods were involved in both studies. 1) The canine angle expressing the vertical position (angle between canine axis and the vertical line perpendicular to the occlusal plane) was registered. 2) The crown morphology indicating rotation of the canine, as well as the maturity of the canine (Nolla Score System), were registered. Results: The cross-sectional study demonstrated that the largest canine angles were observed in the most mature canines, often with the canine crown appearing in the lateral view. The longitudinal study demonstrated in 4 out of the 14 cases that the canines moved in the vertical plane towards a more upright position, resulting in a smaller angle, while the other ten cases moved during the observation period to a lower and more horizontal position, creating a larger angle. The crown morphology was unchanged in the uprighting cases, while rotation occurred in the ten cases undergoing increasing inclination. Maturity increased during all observation periods. Conclusions: This study is the first study which demonstrates and accordingly proves the hypothesis that the vertical movements and rotation of mandibular canines can occur in children and young adults diagnosed with ectopic mandibular canine eruption. These spatio-temporal movements are believed to be of importance for diagnostics and treatment planning of ectopic mandibular canines.