Chronic migraine is a relatively common disorder in neurological terms that causes very significant disability at a high cost. The precise mechanisms behind the progression of episodic migraine to chronic migraine are not well understood. Functional neuro-imaging works on the basis that neuronal activations are associated with changes in regional cerebral blood flow, and it can help us answer some of these questions. In this review, we discuss important recent studies in chronic migraine or studies relating to increasing frequency of migraine attacks. The findings show that increasing frequency of migraine attacks is associated with changes in key brainstem areas, basal ganglia and various cortical areas involved in pain.