The current invention provides methods to identify γ9δ2T-cell receptors (γ9δ2TCR) that mediate anti-tumour responses. Surprisingly, it was now found that the CDR3 regions of the γ9-T-cell receptor chain and the δ2-T-Cell receptor chain (δ2TCR chain) are of importance. Based on these findings, combinatorial-γδTCR-chain-exchange (CTE) is proposed as an efficient method for identifying γ9δ2TCRs that mediate anti-tumour responses. Using the method of the invention, specific sequences of the respective γ9TCR and δ2TCR chains were identified that mediate anti-tumour responses. Hence, the invention further provides for specific γ9δ2TCRs, or fragments thereof, that may be used e.g. in diagnostics or treatment of cancer. The invention further provides for nucleic acid sequences, genetic constructs and retroviral vectors that can be used to express the γ9δ2TCRs according to the invention.