This study documents the cost of immediate and delayed DIEP flap breast reconstruction. Immediate reconstruction is more attractive from an economic perspective since it only requires one operation, one anaesthetic procedure and one recovery period in hospital. From the perspective of healthcare budget management, assessing the possible cost savings from immediate reconstruction yields interesting results. Since charges do not reflect the real costs of providing care, we calculated resource costs using the micro-costing method. About 95% of the initial mastectomy costs could be saved when performing an immediate breast reconstruction. This was about 35% of total standard direct and indirect costs due to mastectomy and delayed breast reconstruction. In a growing cost conscious environment of managed care, the economic evaluation should, therefore, encourage the trend towards more immediate reconstructions.