In this study, we evaluated the possible role of Growth Hormone Receptor (GHR) expression pattern in determining rectal cancer radiosensitivity. We examined GHR expression in pre-treatment biopsy materials and post-operative specimens from 98 patients by immunohistochemistry (IHC) and reverse transcription-polymerase chain reaction (RT-PCR). GHR expression was evaluated for association with tumour radiosensitivity, which was defined according to Rectal Cancer Regression Grade (RCRG). IHC results demonstrated that GHR overexpression was significantly associated with a poor response to radiotherapy (P < 0.001, r(s) = 0.399); RT-PCR detection of GHR expression on pre-radiation biopsy specimens also showed that GHR mRNA negative group had a higher radiation sensitivity (P < 0.001, r(s) = 0.398). Compared with the pre-radiation biopsy specimens, the paired post-operative specimens showed a significantly up-regulated GHR expression in the reliquus cancer cells (P < 0.001). In conclusion, GHR expression levels may be an indicator for rectal cancer radiosensitivity before pre-operative irradiation. The administration of GHR antagonist may have the potential to increase rectal cancer radiosensitivity.