The diagnostic work-up for a cancer of unknown primary site is guided by the clinical presentation as well as the histology of the metastases.  The detection of a primary site is important to guide therapy and improve prognosis.  Using a series of case examples, the current role of imaging in the management of cancer of the unknown primary will be explained.  The role of newer modalities including whole body MRI and PET/CT will also be reviewed as well as the limitations of these modalities.  The future possibilities of functional imaging using different radiotracers and the integration of PET/MRI will also be discussed.