The optimal position of the condyle in glenoid fossa is a fundamental question in dentistry. There is no quantitative standard for the optimal position of mandibular condyle in the glenoid fossa in Vietnamese. The purpose of this study is to assess the position of the condyle by cone beam computed tomography (CBCT) images in 40 class I skeletal patients (18 males and 22 females) with normal function of temporomandibular joint (TMJ). In this cross-sectional study, the authors evaluated the joint by measuring the joint spaces on true sagittal plan (the anterior (A), superior (5) and posterior (P) joint spaces) and true coronal plan (the medial (M) and lateral (L) joint spaces), then calculating the NP ratio, SIP ratio and MIL ratio. A paired t-test and independent samples t-test were employed for analysis. The result showed that the superior (S) posterior (P) the anterior (A) joint spaces on sagittal plan, and the medial (M) lateral (L) joint spaces on coronal plan. There is no difference between two sides. The posterior spaces in males are large than in females (p 0.005). The data from this study could be a useful and comparable reference for the clinical assessment of condylar position in patients with normal functional joint.