Purpose: Giant intracranial aneurysms commonly cause poor clinical outcome and few studies focus on them. This study is to retrospectively report the angiographic and clinical presentations in unruptured giant saccular vertebrobasilar aneurysms with and without endovascular treatment. Methods: Out of 400 patients who had unruptured posterior circulation aneurysms in a single center, we found 10 unruptured giant (>25 mm) saccular vertebrobasilar aneurysms. Clinical and angiographic presentations as well as their clinical outcomes were assessed. Results: Of the 10 giant aneurysms in 10 patients, three were left untreated. During 6 months follow-up, all 3 of these patients died from aneurysm rupture. The remaining 7 patients were treated by endovascular procedure, 5 received stent-assisted coiling, 1 was treated by parent artery occlusion (PAO), and 1 was treated by conventional coiling. Of these treated patients, only one survived during a 22 month period of follow-up. Conclusions: Patients with giant saccular aneurysms of vertebrobasilar artery presenting mass effect may have extremely poor clinical outcomes and may not benefit from endovascular treatment. (C) 2016 Polish Neurological Society. Published by Elsevier Sp. z o.o. All rights reserved.