Objective: To compare the diagnostic accuracy of ultrasound (USA) and non-contrast (CT) CT in the detection of ureteral stones in the determination of patients having acute flank. Study Design: A standardized double-blinded study. Place and Duration: In the Radiology Department of Jinnah Hospital, Lahore for one-year duration from February 2018 to January 2019. Methodology: One hundred and twenty-four patients with flank pain for 1 year were examined with non-contrast ultrasound and CT Scan. Both techniques have been used to determine the presence and location of the ureter stone and the presence or absence of secondary symptoms such as ureteral and calyceal dilatation, knitting of the periureteric fat, and the sign of soft tissue margin. Results: 86 of 124 patients were confirmed to be ureteral stones on urological intervention or on ultrasound confirmation. Ultrasound showed specificity of 95% and sensitivity of 93% in the diagnosis of ureterolithiasis. CT showed specificity of 95% and sensitivity of 91%, respectively. Conclusion: Due to non-invasive and low-cost modality, we recommend that ultrasound be used for the first time and ultrasound is not suitable than computerized tomography may be beneficial for diagnosis. Key Words: ultrasound, computed tomography, renal colic.