Purpose: To quantify the impact of immediate reconstruction on radiotherapy planning after modified radical mastectomy & to study radiotherapy complications. Patients and methods:After surgery, patients submitted to adjuvant radiotherapy with irradiation technique assessment using a semi-quantitative score evaluating the design of radiation fields including five objectives: breadth of chest wall coverage, homogeneity, minimization of lung irradiation, avoidance of heart and Dmax. with assessment of radiation morbidity.Results: 30 patients were enrolled at Bristol Haematology & Oncology Centre (UK) and Oncology Department, Ain Shams University hospitals (Egypt) between November 2007 and November 2009, with a mean follow up of 14.4 months. 27 patients (90%) had Latissimus Dorsi flaps & 3 (10%) had TRAM flap. The analysis revealed compromise in 24% of the plans; all are moderate compromise. Reconstruction was noticed to compromise chest wall coverage in 27%. Dose homogeneity, Dmax. and minimizing irradiated lung and heart were not affected. Compromises were more common in left side while complications were grades 1 and 2 without major morbidities. Conclusion:Immediate reconstruction may limit treatment planning of postmastectomy radiotherapy, particularly in providing adequate chest wall coverage; so candidate patients for immediate reconstruction should be aware that the presence of the reconstructed breast could cause technical difficulties.