Aim: The purpose of this research is in increasing the accuracy of determining the tongue position, the amount of space occupied by the tongue and space free from tongue, that information will help to increase of efficiency of diagnostics of dentofacial anomalies in patients, based on cone-beam computer tomography (CBCT) analysis conducted in transversal, sagittal and coronal planes. Material and Methods: Clinical and x-ray examination and orthodontic treatment underwent in 65 patients with anomalies of the dentition complex. Patients divided into two groups. Group 1 - 25 patients aged 12 to 17 years. Group 2 - 40 patients aged 18 to 40 years. All patients underwent CBCT examination before, and during the retention period of treatment. Diagnostic examination carried out by the proposed method for diagnosing the anatomical and functional state of the dentition complex. After drawing up a treatment plan all patients underwent orthodontic treatment, which included the upper jaw expansion, using various orthodontic appliances. This method of CBCT diagnostic allows to identify anomalies in the position of the tongue before and after orthodontic treatment, to assess the quality of orthodontic treatment, based on the analysis of not only the tongue filling the space of the dome of the palate, but also the position of the bone structures of the skull in three planes. Results: The study results showed that not all of the patients carried out recovery of the anatomical and functional balance of the maxillofacial complex after orthodontic treatment, suggesting the need for more myogymnastics and speech therapy training of the tongue before, during, and after treatment.