Neurosurgeons have an especially high rate of exposure to serious ethical challenges in their line of work. The aim of this study was to assess the type and frequency of ethical theories used by neurosurgery residents to make extra- ethical decisions in challenging situations and their relation with the level of residency, and curricular training about medical ethics. A total of 12 neurosurgery residents in Mashhad University of Medical Sciences were interviewed; all the participants were male and aged 29–40 years (...) old. Of all, six were senior and six were junior. Using a systematic review of neurosurgery and medical ethics textbooks, five common cases were selected and a semi-structured, open-ended interview was developed. The interviews were digitally recorded and analyzed in two separate stages. Comparison of the results of the two stages led us to the final judgment about the dominant ethical theory used in each case. In all 60 cases, the decision-making process was compatible with either Deontology or Consequentialism. Only in two cases, beside Deontology, the Virtue ethics was used as an alternative in special situations. The ethical theories were not consistent for all the 12 subjects and all the five questions. No statistically significant difference was found between senior and junior residents, neither for each question nor for the aggregate. Only one of the subjects had extracurricular training in medical ethics, consequently precluding further analysis. Although not intended to be evaluated by this study, similar heterogeneity was observed in final decisions. When faced with medical ethics challenges, neurosurgery residents did not follow a consistent ethical theory for making decisions. The type and frequency of theories did not seem to be changed during the residency period. (shrink)