Few articles have been written about the flexor tendon sheath ganglion in the finger, especially, between A1 pulley and A2 pulley. We report on rare cases of flexor tendon sheath ganglion with one symptomatic and two asymptomatic. All masses were evaluated using real-time ultrasonography and well-defined anechoic cystic lesions with posterior enhancement were observed. A 17-year-old female had a small mass at the 4th metacarpophalageal joint of her right hand, with pain and triggering. The patient underwent simple excision and a ganglion measuring 1.0x0.8 cm in size was derived from Camper's chiasm, between A1 pulley and A2 pulley. In two asymptomatic cases, ganglia measuring less than 0.5 cm in size observed. Based on our experience, real-time ultrasonography would be an excellent diagnostic modality in determining the treatment method in flexor tendon sheath ganglia, and surgical excision is recommended in symptomatic, especially triggering patients.