This chapter discusses the role of structural imaging using CT and MRI, conventional angiography and CT angiography, and physiological imaging using CT perfusion, 131Xenon CT, MRI and magnetic resonance spectroscopy (MRS), single-photon emission computed tomography (SPECT) and positron emission tomography (PET) in the assessment, management and prediction of outcome neurological injury. Acute CT is useful in identifying those individuals in whom deterioration is as a result of a mass lesion and can demonstrate extradural, subdural or intracranial haemorrhage and midline shift, or subarachnoid haemorrhage and ventricular abnormality. Contrast-enhanced CT imaging is also used to produce CT angiography and perfusion imaging. MRI data are produced using powerful static magnetic fields and intermittent oscillating radiofrequency electromagnetic fields that elicit signals from the nuclei of certain atoms. Single-photon emission CT uses conventional gamma-emitting nuclear medicine isotopes with multiple detectors to generate tomographic images.