Behavioral tasks requiring visual-spatial discrimination such as line bisection are used clinically to assess right hemisphere function, yet the anatomical substrate of line bisection has yet to be elucidated by functional imaging. In the current study, nine right handed, healthy adult subjects underwent split-dose technetium-99m-hexamethylpropylene amine oxime single photon emission tomography during performance of two visual tasks. Statistical parametric maps that represented significant changes in regional cerebral blood flow (rCBF) for each task were generated. Increases in rCBF were seen in the right dorsolateral prefrontal cortex, the insula, and the superior temporal lobe with a line-bisection discrimination task, whereas increases in the visual association areas, the posterior cingulate gyrus bilaterally, and the anterior cingulate gyrus on the right were seen with a similar control task which required sustained visual attention, but no visual spatial discrimination. We conclude that distinct areas in the nondominant hemisphere can be shown to be active during performance of line-bisection discrimination and sustained visual attention.