Background. To define risk factors for the multiplicity of cerebral aneurysms, as well as clinical and therapeutical characteristics of patients with single aneurysms (SA) and multiple aneurysms (MA). Methods. Retrospective study on 95 patients with SA and 22 patients with MA. For patients with SA and MA the following parameters were compared: gender, age, clinical state, aneurysmal localization and size, incidence of rebleeding and vasospasm, manner and outcome of treatment, preoperative interval, intraoperative rupture and postoperative complications. Results. Aneurysms on anterior communicating artery existed in 37.4% of SA and in 17.8% of all MA (p<0.05). As much as 44.2% of all aneurysms on middle cerebral artery and only 19% of all aneurysms on anterior communicating artery were associated with some other aneurysm (p<0.02). The average size of SA was 15.4 ± 11.8mm, and 9.8 ± 9mm for MA (p<0.05). Surgery was performed in 77.3% of patients with MA and 78.9% of patients with SA (p>0.05), but complete surgical clipping was performed in 89.3% of patients with SA and in 47.1% of patients with MA (p<0.01). Among operated patients with MA and SA, intraoperative rupture occurred in 36% and 17.6% of cases, respectively (p<0.05) and ischemic postoperative complications were found in 29.4% and 17.3% of the cases (p>0.05). Among 72.7% of all patients with MA and in 69.5% of all patients with SA the outcome was good, while among surgically treated patients it was good in 76.5% and 70.7% of cases, respectively. Conclusion. The treatment outcome was similar for patients with MA and SA, but complete operative treatment is significantly more frequent for SA. Multiple aneurysms were considerably smaller and with different anatomical distribution in relation to solitary aneurysms.