Purpose: Patient preferences for health states can be measured with the standard gamble (SG), time trade-off (TTO), visual analogue scale (VAS), and willingness to pay (WTP). Preference testing can be cognitively demanding and may be affected by cognitive functioning. We measured preferences in patients with cerebral aneurysms, a population vulnerable to cognitive deficits related to aneurysm rupture or treatment. Methods: A cross-sectional cohort of neurosurgery clinic patients with cerebral aneurysms completed the SG, TTO, VAS, WTP and the Mini Mental State Exam (MMSE) during a face-to-face interview. We recorded instances when patients had difficulty understanding or completing preference assessment. We examined the relationship between preferences and cognitive impairment or difficulty with testing using the Mann-Whitney U test. Multivariate linear regression models examined the relationship between preferences and patient characteristics, aneurysm history, cognitive impairment, and difficulty with preference assessment. Results: One hundred sixty-five patients completed all 5 instruments; their mean age was 54.2 years, 72% were women, 52% had a history of aneurysm rupture, 68% had previous aneurysm treatment, and 7% had MMSE scores <24, consistent with cognitive impairment. Twenty patients (12%) had difficulty with preference assessment according to the examiner, although those patients still completed all preference instruments. In the univariate analyses, patients with cognitive impairment had lower scores on the VAS (mean=0.55 vs. 0.68, P=0.045), and patients with assessment difficulties had lower values on the SG (mean=0.63 vs. 0.80, P=0.003) and WTP ($199,100 vs. $104,700, P=0.087). Regression models showed that cognitive impairment was associated with lower preferences measured with the SG (&beta= -0.23, P=0.004), TTO (&beta= -0.18, P=0.087), and VAS (&beta= -0.12, P=0.032), and that difficulty with preference assessment was independently associated with lower preferences measured with the SG (&beta= -0.17, P=0.004), TTO (&beta= -0.17, P=0.087) and WTP (&beta= $116,400, P=0.032). WTP preferences were also independently associated with income (&beta= 2.1, P<0.001). Conclusions: Cognitive impairment and difficulty with preference assessment are independently associated with lower preference values in patients with cerebral aneurysms. Cognitive changes may affect preferences directly, and/or may induce downward bias during preference assessment. Difficulty understanding or completing the preference elicitation procedures may also produce a downward bias in preference values. Utility assessments may want to incorporate both formal cognitive testing and interviewer judgments regarding subjects' comprehension.