This study was performed in order to investigate the influence of the vertical dimension on the occlusal plane angle. Cephalometric tracing were made from sideview headfilms from a sample of 150 patients consulting at the consultation and treatment center in Rabat, Morocco. This sample group included 60 males and 90 females. The aims of our research were to study statistically the impact of the vertical dimension on the occlusal plane angle and to check the validity of the Wits (Ao-Bo) by evaluating the impact of the vertical dimension on the Wits and by comparing it with the AF-BF value (Ao-Bo/Frankfurt) proposed by Chang.