Brain lesion studies demonstrated that the right ventral frontal/anterior insular cortex (r-VF/AI) and its functional connectivity (FC) can play an important role in belief evaluation and delusions of various content.Objective: to test the hypothesis about the associations between the functional characteristics of this region and delusions in patients with mental disorders.Material and methods. The sample included 16 patients with delusional disorder and paranoid schizophrenia. We analyzed the whole-brain FC of the r-VF/AI as well as the local coherence and amplitude of low-frequency fluctuations of BOLD signal in this region.Results. The “Conviction” item of the Brown Assessment of Beliefs Scale was positively correlated with the FC between the region of interest and a cluster in the right occipital cortex (located predominantly in the occipital fusiform gyrus and the occipital pole and slightly extending to the lingual gyrus and inferior lateral occipital cortex). Local coherence and amplitude of low-frequency fluctuations in the region of interest were not associated with clinical characteristics related to delusions.Conclusion. The correlations of delusional conviction with FC between the regions involved in belief evaluation and visual perception may reflect aberrant top-down/bottom-up or cyclic processes described within the Bayesian models of delusions.