Background: Diagnosis of carpal tunnel syndrome is based on clinical findings and these findings are used to confirm the diagnosis. Sonography is also a noninvasive method for diagnosis of carpal tunnel syndrome. The purpose of this study was to investigate the role of sonography and electrodiagnostic studies in diagnosis of this syndrome. Methods: In a prospective study, 76 hands with diagnosis of carpal tunnel syndrome (study group) were compared with 80 hands (control group) in a training hospital in Kerman-Iran. In both groups the diameter of median nerve was measured by sonography and electrodiagnostic studies were performed only on the study group. The study group, post surgery, was followed up for 6 months and the DASH preoperative functional scoring was compared with post operative scores. Results: The difference between the diameters of the median nerve measured by sonography (p=.0001) and also the difference between before and after-operation Dash Score in the patient group (p=.001) were statistically significant. Sonography was 95% sensitive and 93% specific for the diagnosis of carpal tunnel syndrome. A weak correlation was found between the severity of the disease in electrodiagnostic studies and sonography (p < .01, r=.38). No correlation was proved between the sonographic or electrodiagnostic findings and Dash score before and after the operation (p≥.05). Conclusion: sonography might be a suitable module for the diagnosis of carpal tunnel syndrome, but there were no correlation between its findings or electrodiagnostic findings and functional scores. Whether or not sonography could be substitute for electerodiagnostic tests, will need further investigation.