Reliable assays that could assess treatment response more rapidly or even predict responsiveness of breast tumours to chemotherapy would be very valuable as they would allow for adjustment of ineffective treatment and discontinuation of ineffective treatment in an early phase. As with effective cancer therapy, changes in tumour physiology, metabolism and proliferation do often precede volumetric changes routinely measured by morphological imaging modalities, for example, radiography and computerized tomography, assessment of these parameters by means of single photon emission computerized tomography (SPECT) or positron emission tomography may provide more sensitive and earlier markers of tumour cell death or growth inhibition. This paper reviews the available literature on the role of SPECT and PET in the measurement and visualisation of breast tumour metabolism (glucose utilization and protein synthesis rate), apoptosis induction and chemotherapy resistance mechanisms as predictors or early markers of tumour response or non-response to chemotherapeutic options in patients suffering from breast carcinoma.