Introduction: The intracranial lesions in the third ventricle can have a variety of clinical manifestations. Masses related to the anterior recesses or floor of the third ventricle may manifest as dysfunction of the hypothalamic–pituitary hormonal axis. Masses of the posterior wall of the third ventricle, foramen of Monro masses, and intraventricular masses often manifest as hydrocephalus accompanied mostly by headaches. Some congenital cysts or acquired abnormalities, such as cavum veliinterpositi cyst and ectatic basilar artery, respectively, may be incidental imaging findings but distort the normal anatomy of the third ventricle or mimic more serious disease. Objective: 41 Patients (24 female, 17 male, age 12-82 years) with occlusive hydrocephalus due to intraventricular processes were treated with endoscopic technique with the aid of neuro-navigation. Methods: In these cases, the endoscopic cysto-ventriculostomy and biopsy of lesion has been selected as operative method. The neuro-navigation has been used for the optimization of the operation approach. For diseases in the region of the 3rd ventricle there are three variants: micro neurosurgery, stereotaxy, and endoscopic method. In patients with unclear diagnosis and other clinically limiting conditions the endoscopic guided method as a minimally invasive method should be selected. Results: With the endoscopic method, the intraventricular processes could be visualized. A necessary haemostasis could be performed under direct vision. In addition to the biopsy extraction, the occlusive hydrocephalus could be also treated with this method in approximately 68.3 % of the patients. There were no significant complications or bleedings postoperatively. There was in 70-90% of the cases a reliability of histopathological diagnosis. In comparison with the stereotactic method it has the same grade of accuracy (Mennel et al., 1994, Zentralblattfür Neurochirurgie). There has been no postoperative morbidity or mortality in consequence of this treatment. Conclusions: Neurovavigation-assisted, endoscopic biopsy and cystoventriculostomy has in comparison with the stereotactic method the same grade of accuracy and reliability. It has also more advantages, such as visualization of the operation area and intraoperative treatment and avoidance of complications postoperatively, especially intracranial or intracerebral haemorrhages. The hydrocephalus can also be treated concurrently in the most cases.