Background: The definitive diagnosis of pleural malignancy depends upon histological confirmation by pleural biopsy. Objective: To compare chest U/S and chest CT findings of undiagnosed pleural effusion before medical thoracoscopy to examine the concordance and discordance between them. Patients and Methods: This study was conducted on 30 patients admitted at the Department of Chest Diseases, Al-HusseinUniversityHospital during the period between January 2021 and June 2021. Results:Chest CT was superior to chest ultrasound in the detection of pulmonary nodules, mediastinal lymphadenopathy and mediastinal shift. However, CT findings missed by U/S did not affect the procedure conductance, technique or outcome. Chest U/S was superior to CT chest in the detection of multiloculations, septations, diaphragmatic pleural nodules and visceral pleural nodules. These findings, detected by ultrasound, were consistent with the operative findings. The most common complications of medical thoracoscopy in the study were subcutaneous emphysema in 16.7%, failure of full lung expansion in 10 %, and intractable cough in 3.3% of patients. Conclusion: Sonography overcame the shortcomings of CT, as it used no ionizing radiation, being portable and could be performed while the patient was in the supine, sitting and lateral decubitus positions. U/S has the capacity to clarify the nature of pleural effusions and underlying abnormalities.