Carpal tunnel syndrome is diagnosed based on history, physical examination, and nerve conduction testing; however, there are no clear criteria for the diagnosis of carpal tunnel syndrome. Recently, studies have aimed to diagnose carpal tunnel syndrome through ultrasound or MRI. The purpose of this study was to compare and analyze the cross-sectional area of the median nerve between patients with carpal tunnel syndrome and a control group.From July 2015 to August 2017, we retrospectively analyzed fishery and white-collar workers (164 people, 37 men, 127 women). Carpal tunnel syndrome was diagnosed on the basis of both physical examination and nerve conduction testing. A negative result in either test led to exclusion from the study.In total, 164 wrist MRI were retrieved, with 67 patients diagnosed with carpal tunnel syndrome and 97 patients allocated to the control group. The mean value of cross-sectional area at the pisiform was 18.8 mm in the MRI of the carpal tunnel syndrome patients and 12.1 mm (p-value <0.05) in the control group. The mean value of cross-sectional area at the hook of hamate was 11.70 mm and that at the control group was 11.67 mm (p-value 0.055).Cross-sectional area at pisiform in MRI is a valuable factor in the diagnosis of carpal tunnel syndrome and in predicting the duration of pain.