Introduction: Common bile duct stone (CBDS) is a common clinical problem that can cause serious complications, such as acute cholangitis and pancreatitis. It is important to have an accurate, safe, and reliable method for the definitive diagnosis of CBDS before proceeding to therapeutic endoscopic retrograde cholangiopancrea-tography (ERCP). Objective: To compare the accuracy of trans-abdominal ultra-sound (TAUS) as a diagnostic tool at our institution—Kurdistan Centre for Gastroen-terology & Hepatology (KCGH)—with invasive tool like ERCP in the diagnosis of bile duct stones, using specificity, sensitivity, and positive and negative predictive values. Patient and Method: After obtaining ethical committee approval & informed consent from every patient. This was a prospective study conducted on 71 patients (24 male patients and 47 females patients) where suspected to have CBDS depending on history, clinical suspicion and blood tests. Their ages range between (2 - 88 years). Both TAUS and ERCP were performed. Final diagnosis was confirmed de-pending on ERCP as it served as a diagnostic standard in diagnosing CBDS. Result: In 71 patients suspected to have CBDS by TAUS, only 46 patients had stone (65%), and 55 patients had stone by ERCP (77%). In our result, sensitivity, specificity, pos-itive predictive value and negative predictive value for TAUS were 80%, 87.5%, 65.5% and 56%, respectively. Conclusion: TAUS can play an important role as an initial screening procedure for CBDS detection because of the various advantages like easy availability, cost effectiveness, no requirement of contrast material and lack of ionizing radiation but should done with other imaging modality to avoid se-rious complication of ERCP.