Purpose:To investigate the utility of palmar bowing of the flexor retinaculum (PBFR) on magnetic resonance imaging (MRI) as an adjunct to presurgical evaluation of carpal tunnel syndrome (CTS). Materials and Methods:The CTS group comprised 48 women with CTS diagnosed from clinical history, physical examination, and electrophysiological findings. Another 21 healthy women with no symptoms of CTS served as controls. The CTS group was divided into four subgroups based on symptom duration. CTS patients were preoperatively assessed for symptom severity using a Likert scale. In both groups, palmar bowing of the flexor retinaculum (PBFR) was measured on MRI. Furthermore, relationships with disease duration, subjective symptom severity, and electrophysiological findings were assessed in the CTS group.Results: Although PBFR increased significantly in all CTS groups when compared to the control group, PBFR in patients who complained of severe pain tended to exceed that in patients with mild to moderate pain. Statistical analysis showed a positive correlation between PBFR and pain severity. In contrast, PBFR did not reflect median nerve function.Conclusion: PBFR as seen on MRI seems to correlate significantly with patients' subjective reports of pain severity.Key Words: carpal tunnel syndrome; magnetic resonance imaging; palmar flexor bowing of flexor retinaculum; pain severity.