Abstract Subarachnoid haemorrhage (SAH) is a life-threatened disease with poor outcome. It is usually caused by an intracranial aneurysm (IA) rupture and rapid diagnosis and treatment are of great importance. Computed tomography (CT) is a reliable method to detect the blood in the subarachnoid (SA) spaces. Digital subtraction angiography (DSA) offers dynamic and morphological information of a ruptured IA. The treatment options for excluding an aneurysm from the main circulation are neurosurgical clipping and endovascular procedures. The purpose of the present study was to evaluate the risk factors of acute hydrocephalus (HC) and the reliability to localize the ruptured aneurysm based on non-contrast CT. The aim was also to compare the effect of neurosurgical and endovascular treatment on the development of chronic HC, and evaluate the incidence and the risk factors of early rebleeding (<  30 days) after coiling. The data of 180 operated patients with a ruptured IA were checked. Two neuroradiologists separately located the IAs based on non-contrast CT. The analyses of blood amount and distribution was a reliable method for estimating the location of ruptured middle cerebral artery (MCA) aneurysms and anterior communicate artery (ACoA) aneurysms. Intracerebral haemorrhage (ICH) was a predictor for detecting the precise site. The results confirmed that intraventricular haemorrhage (IVH) was the most consistent single risk factor for the development of acute HC. Haemorrhage in the basal region and the large total blood amount in the SA spaces were strong predictors. The effect of early treatment modality for ruptured IAs on the development of chronic HC with 102 clipped and 107 coiled patients was compared. The treatment method used was not significantly associated with the occurrence of chronic HC or the need for shunt operation. The incidence and risk factors of early rebleeding after coiling were investigated in 194 consecutive acutely (within 3 days) coiled patients with ruptured IAs. The incidence of early rehaemorrhage was 3.6%. The presence of ICH at admission and poor clinical condition were significant predictors for rebleeding. An early rehaemorrhage appeared as an enlargement of the ICH in all of these patients. In conclusion, the non-contrast CT is a reliable method to detect the location of ruptured IA in patients with MCA and ACoA aneurysms. The risk factor for the development of acute HC is IVH. Other predictors are the total SA blood amount and blood in the basal regions. The treatment method used for acutely ruptured IA has no significant effect on the occurrence of chronic HC. The incidence of early rebleeding after coiling is low. The risk factors of rebleeding are the presence of ICH and poor clinical condition. Rehaemorrhage appears often as an enlargement of the ICH.