Cyst of the canal of Nuck is a rare cause of inguinal swelling in woman. We report a case of a cyst of the canal of Nuck in which sonography showed a tubular cystic structure with internal septae localized within the inguinal canal. Magnetic resonance examination demonstrated that the mass was hypointense on T1-weighted and hyperintense on T2-weighted series and that there were fine hypointense septae inside the mass on the T2-weighted sequence. Diagnosis of cyst of the canal of Nuck was confirmed by surgery and subsequent histopathologic evaluation.