Object Terson's syndrome (TS) is a vitreous hemorrhage in association with subarachnoid hemorrhage (SAH). Its diagnosis is often delayed, which may result in vision loss secondary to treatable conditions. Methods to hasten early diagnosis and consequent ophthalmic referral are desirable. The aims of this study were 1) to assess the specificity and sensitivity of conventional head CT for diagnosing TS in patients with aneurysmal SAH (aSAH); and 2) to determine the incidence of TS and its association with age, sex, aSAH severity, and overall mortality. Methods Patients admitted to Helsinki University Central Hospital who underwent surgery or endovascular treatment for a ruptured intracranial aneurysm during 2011 were participants in this prospective study. They underwent serial dilated fundoscopic examinations during a 6-month period. Two radiologists independently reviewed ocular findings suggestive of TS on conventional CT head scans obtained in all patients as a routine diagnostic procedure. Associations between TS and relevant clinical, radiological, and demographic data were analyzed with uni- and multivariate logistic regression. Results Of 121 participants, 13 (11%) presented with TS, and another 22 (18%) with intraretinal hemorrhages. For reviewing CT head scans, the overall observed agreement between the 2 raters was 96% (116 of 121 cases), with a substantial κ of 0.69 (95% CI 0.56–0.82). The sensitivity of the CT findings for TS was 42%, and the specificity was 97%. Associations of the World Federation of Neurosurgical Societies (WFNS) and Hunt and Hess grades on admission, the presence of intracerebral hemorrhage, female sex, and aneurysm length with TS were all statistically significant. Logistic regression demonstrated that sex and WFNS grade were independently associated with TS and provided the best fit to the data. Conclusions Routinely looking for TS findings in CT head scans may prove valuable in clinical practice. Terson's syndrome is associated with female sex and poor clinical condition on admission.