BACKGROUND: Generalized anxiety disorder (GAD) is a prevalent anxiety disorder, but its neurobiological basis has been poorly studied. A few cognitive models have been proposed for understanding GAD development and maintenance. The aim of this study is to review functional Magnetic Resonance Image (fMRI) studies conducted with GAD patients and evaluate if they support and underpin the theoretical cognitive models proposed for this anxiety disorder. METHODS: A literature systematic review was undertaken in PubMed and ISI databases with no time limits. RESULTS: From the studies included in this review, 10 explored the "emotional dysregulation model", showing, prefrontal cortex (PFC) and anterior cingulate cortex (ACC) hypofunction and deficient top-down control system during emotion regulation tasks, despite conflicting techniques and results. Only one study explored the "conditioned fear overgeneralization theory", other the "intolerance of uncertainty model" and two studies were unspecific (worry induction tasks). Between those, there were 4 studies evaluating pre- and post-treatment with antidepressants or "mindfulness". LIMITATIONS: The studies? methodologies differ between one another making it difficult to identify a common finding. CONCLUSION: Emotion dysregulation seems to be an important cognitive dysfunction in GAD patients and fMRI studies suggest that it is related to PFC and ACC hypofunction as well as a deficient cortex-amygdala functional connectivity.