Introduction: Thyroid gland behind the sternum near the base of the neck, and it is one of the gland behind the sternum at cartilage southern centre of middle mediastinum and at back of superior middle mediastinum rarely [ R.E Gabunia.,E.K.Kolesnicova.,L.B.Tumanov.,1983; J.O.Shepard.,1991; S.K.Wernecke 1991; N. B.Litvakovskaya.,1994;V.P.Harchenko.,P.M.Kotlyarov.,R.V.Kertanov.,Z.S Tsallagova., 2002]. Goal: The research thesis aims to make diagnosing and identifying the nature and symptoms of thyroid gland behind the sternum by roentgen, US and computer tomography and developing the criterion characteristics of diagnostics. The following objectives will be resolved in order to implement the goal of research thesis: 1. To identify the symptoms of thyroid gland behind the sternum which is obtained by the roentgen? 2. To identify the symptoms of thyroid gland behind the sternum by diagnostics of US and computer tomography 3. Developing the criterion characteristics of thyroid gland behind the sternum by diagnostics of US, computer tomography and the roentgen Materials and Methods: Made conclusion at symptoms identified by diagnostics of US, computer tomography and the roentgen at 12 patients who were diagnosed with thyroid gland behind the sternum through 2005-2011. The diagnostics of thyroid gland behind the sternum was approved by the surgical operation and biopsy analysis which is a medical test involving the removal of tissues for examination. It is the medical removal of tissue from a living subject to determine the presence or extent of a disease under a microscope by a pathologist. Results: The symptoms of 12 patients who were diagnosed with thyroid gland behind the sternum were identified by diagnostics of US, computer tomography and the roentgen. From the symptoms defined by roentgen images of thyroid gland behind the sternum, located in western upper south part of middle mediastinum (P<0.001), oval shaped thyroid (P<0.05), calcification osteoporosis (P<0.01), bronchus was pushed to healthy side (P<0.05), changes of middle mediastinumwas moved upward when cough, drink and make Valsalve’s test /a method for testing the patency of the Eustachian tubes. With mouth and nose kept tightly closed, the patient makes a forced expiratory effort (P<0.01) therefore there is true statistical probability. Conclusions: 1. During the thyroid gland behind the sternum, the additional changes are identified at thyroid gland behind the sternum, located in western upper south part of middle mediastinumat 75.0%, the mentioned changes are moved upward when made cough, drink and make Valsalve’s test by roentgen, lost similarity of structure and pushed the bronchus to healthy side at 66.7%, there is dominant symptoms by roentgen that gullet defined by barium substance was pushed to healthy side at 58.3%. 2. By the ultrasound analysis, during the thyroid gland behind the sternum, the changes are relevant to thyroid and vascularization at 100% , to capsule at 75% and osteoporosis at 66.7%. 3. Changes are relevant to thyroid and vascularization at 100% or oval shape more compactness was identified by the contrast substance , pushed the bronchus to healthy side at 66.7%, there is dominant symptoms by roentgen that bronchus was pushed to healthy side, 4. We established that there is thyroid gland behind the sternum. status of the additional changes of middle mediastinum , compactness, structure, capsule, size, shape of the thyroid gland behind the sternum, additional changes of middle mediastinum changes the location of the nearest organs due to thyroid, so identified the main criterions to diagnose and to identify the thyroid gland behind the sternum by roentgen, US and computer tomography.