Based on the observation of the course of callosal fibres and of their artero-venous support as appearing in a microanatomic study, the Authors propose a variant of standard callosotomy procedure by the introduction of the transverse section of callosal fibres. This technique would allow the surgeon to spare a larger number of callosal fibres by the combined effect of a lower direct mechanical traction on fibres and a lower impact on artero-venous microcircle. The neuropsychological outcome of the patients who underwent this kind of procedure was evaluated. Fourteen patients affected by occupying-space lesions involving the anterior and middle third ventricle were included in the study. Ten patients underwent transverse callosotomy, four subjects received standard sagittal callosotomy. A control group was also included in the study. All patients underwent a pre-operative and six months post-operative neuropsychological evaluation focused on performance at cognitive and attentional tasks. No disturbances in executive function were observed in either group. Patients receiving transverse callosotomy performed as well as control group subjects in attentive tasks, which is not the case of patients undergoing sagittal callosotomy who show a marked deficit in selective attention for left side visual field. The observed more favourable neuropsychological outcome supports transverse callosotomy as a valid alternative method to standard longitudinal callosotomy in third ventricle surgery.