Because the circle of Willis (CoW) supplies blood to the brain in case of occlusion of one of the cerebral arteries, identification of any change in its classical shape could be useful in the assessment of cerebrovascular morbidity. The purpose of our research was to study the anatomical variants of CoW identified on fresh brains obtained at the clinical autopsies of adult deceased patients belonging to a specific population (Northeastern region of Romania), as no data are available for Romania population up to date. The study group included consecutive patients who died in Prof. Dr. Nicolae Oblu Emergency Clinical Hospital, Iaşi, Romania, due to medical causes between January 1, 2014 and June 30, 2016, to whom a clinical autopsy was performed. From a total of 96 circles of Willis, 29.17% presented an atypical morphology. We identified eight types of anatomical variants, which affected simultaneously both the posterior and the anterior parts of CoW in 46.42% of cases. The most frequent anatomical variants were hypoplasia (20.91%), followed by the absence of an artery (3.06%), and partially fetal type artery (2.04%). 67.86% of atypical CoW exhibited more than one anatomical variant of an artery in one circle. We identified nine of the 23 morphological patterns that were published to date, and also nine new types. Our research proved that in the population living in the Northeastern part of Romania the anatomical variations of circles of Willis are very polymorphic, with particular morphological aspects.