Alterations of cyclin D1, one of the main regulators of the cell cycle, are known to be involved in variouscancers. The CCDN1 G870A polymorphism causes production of a truncated variant with a shorter half-life andthus thought to impact the regulatory effect of CCDN1. The aim of the present study was to contribute to existingresults to help to determine the prognostic value of this specific gene variant and evaluate the role of CCDN1G870A polymorphism in brain cancer susceptibility. A Turkish study group including 99 patients with primarybrain tumors and 155 healthy controls were examined. Genotypes were determined by polymerase chain reactionrestrictionfragment length polymorphism analysis. The CCDN1 genotype frequencies in meningioma, gliomaand control cases were not significantly different (p>0.05). No significant association was detected according toclinical parameters or tumor characteristics; however, a higher frequency of AG genotype was recorded withinpatients with astrocytic or oligoastrocytic tumors. A significant association between AG genotype and gliobilastomamultiforme (GBM) was recorded within the patients with glial tumors (p value=0.048 OR: 1.87 CI% 1.010-3.463). According to tumor characteristics, no statistically significant difference was detected within astrocytic,oligoasltrocytic tumors and oligodentrioglias. However, patients with astrocytic astrocytic or oligoastrocytictumors showed a higher frequency of AG genotype (50%) when compared to those with oligodendrioglial tumors(27.3%). Our results indicate a possible relation between GBM formation and CCDN1 genotype.