Several lines of evidence indicate that the neural network that underlies the pathophysiology of obsessive-compulsive disorder and depression centers on the prefronto-basal ganglia system. Particularly involved are anterior cingulate cortex, the orbital prefrontal cortex, the ventral striatum, and parts of the thalamus. Additional integral parts of the network include, the amygdala, the midbrain dopamine cells and the serotonergic neurons. Collectively, these brain regions are involved in various aspects of reward-based learning and good decision-making skills. They are also associated with sadness and depression, pathological risk-taking, addictive behaviors, and obsessive-compulsive disorder. Two of the most successful deep brain stimulation targets for obsessive-compulsive disorder and depression are centered in white matter tracts. These targets were chosen for their central location and ability to capture specific ascending and descending connections, with a particular focus on fibers connecting the subgenual anterior cingulate and orbital cortex with the basal ganglia, thalamus, and amygdala. As more knowledge is obtained concerning the details of these connections, more precise targets may be possible.