The purpose of this study is to examine the relationship between psychological factors, regional brain activity and natural killer cell activity (NKA). Eight patients with malignant diseases were studied by FDG-PET under a resting condition. NKA and degree of anxiety and depression were measured using Taylor's manifest anxiety scale (MAS) and Zung's self-rating depression scale (SDS). Linear correlation of NKA and psychological measures to the regional brain metabolism in cancer patients was examined using statistical parametric mapping (SPM). Positive linear correlation between NKA and regional metabolic rate ratios was identified in the visual association cortex, anterior cingulate gyrus (CG) and sensorimotor area, and negative correlation was identified in the inferolateral prefrontal cortex (ILPFC), prefrontal cortex (PFC), orbitofrontal cortex (OFC) and anterior temporal cortex. Positive linear correlation to the MAS score was identified in the visual association cortex, anterior CG, primary sensorimotor area and the posterior parietal cortex, and negative correlation was detected in the ILPFC, PFC, OFC and anterior temporal cortex. The NKA and MAS scores positively correlated with each other (p<0.001). The result might serve as supporting data for a hypothesis that psycho-immune interaction is also mediated by the cerebral cortex and limbic system.