Imaging of tumour response to therapy has steadily evolved over the past few years as a result of advances in existing imaging modalities and the introduction of new functional techniques. The use of imaging as an early surrogate biomarker of response is appealing, because it might allow for a window of opportunity during which treatment regimens can be tailored accordingly, depending on the expected response. The clinical effect of this would ultimately result in a reduction in morbidity and undue costs. The aim of this review is to describe the potential of various new imaging techniques as biomarkers of early tumour response. We have reviewed the literature and identified studies that have assessed these techniques, such as diffusion-weighted MRI, dynamic contrast-enhanced MRI, magnetic resonance spectroscopy, and 18-fluorodeoxyglucose-PET as early response indicators, and highlight the current clinical awareness of their use.