Various factors contribute to the development and maintenance of delusions in the context of schizophrenic psychoses. Studies with functional and structural MRI were able to detect neurobiological correlates of paranoid symptoms. Consistent with the neurodevelopmental hypothesis of schizophrenic psychosis, which implies an early developmental disorder affecting temporo-limbic areas and resulting in a disinhibition of striatal dopamine release, current imaging studies point towards the involvement of temporo-limbic and frontal dysfunction in delusion formation. In line with this, a specific role of dopamine as a neuromodulator in delusion formation is being discussed. Finally, mechanisms relevant to delusion formation appear to involve cognitive processes such as biases of attribution with regard to emotionally salient events as well as attentional biases during the perception of affective stimuli.