Background: The diaphragm is located inferiorly, the thoracic inlet is located superiorly, and the pleural cavities are located laterally to define the mediastinum. According to various anatomists 4 it is further split into anterior, middle, and posterior compartments. Including thymoma, teratoma, thyroid illness, and lymphoma, anterior mediastinal tumours make up 50% of all mediastinal masses.5 While tumours that develop in the posterior mediastinum are frequently neurogenic tumours, middle mediastinum masses are typically congenital cysts. Objectives: 1. To study the computed tomographic characteristics of Mediastinal lesion/masses in Plain and Contrast enhanced scans. 2. To locate, differentiate and diagnose mediastinal masses. Material & Methods: A prospective hospital based observational study. Department of Radio diagnosis, Al Ameen Medical College & Hospital, Vijayapura, Karnataka. All cases referred to the department of Radio-Diagnosis for clinically suspected Mediastinal masses. study consisted of 40 subjects. Purposive sampling technique. All the cases were studied on a SIEMENS ACQUISITION computed tomography machine. Patients were kept nil orally 4 hrs prior to the CT scan to avoid complications while administrating contrast medium. Risks of contrast administration were explained to the patient and consent was obtained prior to the contrast study. Results: CT and Histopathology Diagnosis was Malignant in 90.0%, Benign in 100.0%. CT was Benign and Histopathology Diagnosis was Malignant in 10%. There was a significant difference in CT and HPE classification of mediastinal masses and comparison. Conclusion: we conclude that computed tomography definitely has a major role to play in the evaluation of a mediastinal mass regarding the compartmental distribution, mass effect upon adjacent structure and provisional diagnosis with Sensitivity of 90 % and Diagnostic Accuracy of 97.5%.