Objective: To compare the radiation dose in the supraclavicular lymph node region betweenthree-dimensional conformal radiotherapy（3 D-CRT） and intensity-modulated radiotherapy（IMRT） after radicalmastectomy

and to provide a basis for clinical treatment. Methods: Fifteen postmastectomy patients in our depart-ment were randomly selected

and 3 D-CRT or IMRT was designed for each patient to compare the radiation doses tothe target volume and the organs at risk between the two different radiotherapies. The parameters compared includedradiation dose

homogeneity index（HI）

and conformity index（CI） of the target volume

the ipsilateral lung

thecontralateral lung

the larynx

the humeral head

and the spinal cord. Results: There was no significant differencesin the D95%of the target volume and the radiation doses to the ipsilateral lung

the contralateral lung

and the spinalcord between the 3 D-CRT group and the IMRT group（P > 0.05）. The IMRT group had significantly better HI and CIof the target volume than the 3 D-CRT group（P < 0.05）; the IMRT group had significantly higher radiation doses tothe larynx and the humeral head than the 3 D-CRT group（P < 0.05）. Conclusion: For patients requiring special pro-tection for their larynx or humeral head

3 D-CRT is recommended. For patients requiring special consideration forthe HI of radiation dose in the target volume

IMRT is recommended.