Objective – In vivo structural magnetic resonance imaging (MRI) studies have evaluated the brain anatomy of various psychiatric disorders, allowing the investigation of putative abnormal brain circuits possibly involved in the patophysiology of psychiatric disorders. Here we reviewed the structural MRI literature in mood and anxiety disorders. Methods – All anatomical MRI studies evaluating mood and anxiety disorder patients were identified through a comprehensive Medline search conducted for the period from 1966 to January 2002, and a manual search of bibliographic cross-referencing complemented the Medline search. Results – Differential patterns of anatomical brain abnormalities appear to be involved in subtypes of mood disorders, with hippocampus and basal ganglia being abnormal in unipolar disorder, and amygdala and cerebellum in bipolar disorders, suggesting that these two mood disorders are biologically distinct. As for anxiety disorders, orbital frontal regions and basal ganglia have been reported to be anatomically abnormal in obsessive-compulsive disorder, temporal lobe was found to be abnormally reduced in panic disorder, and abnormal hippocampus shrinkage was shown in posttraumatic stress disorder. Conclusions – The structural MRI findings reviewed here suggest abnormalities in specific brain regions participating in proposed neuroanatomic models possibly involved in the pathophysiology of mood disorders and anxiety disorders. Nonetheless, available MRI studies have suffered from limitations related to relatively small patient samples and involvement of medicated patients, and were largely cross-sectional investigations. Therefore, longitudinal MRI studies involving more sizeable samples of drug-free patients, patients at first episode of illness or at high risk for mood or anxiety disorders, associated to genetic studies, are likely to be extremely valuable to separate state from trait brain abnormalities and to characterize further the pathophysiology of these disorders.