Fas molecule is one of the main important molecules involved in apoptotic cell death. Single nucleotide polymorphisms in the promoter of Fas gene at positions -1377G/A and -670 A/G may affect its expression and play an important role in the pathology of leukemia. In the present study the association between these polymorphisms and risk of the development of acute lymphoblastic leukemia (ALL) in children with ALL compared to cancer-free control subjects was examined by polymerase chain reaction- based restriction fragment length polymorphism. The relationship between the polymorphisms and clinical and laboratory features of the patients and response to therapy were determined. No significant differences in genotype and allele frequencies between the patients and the control subjects at positions -670 and -1377 were detected. Evaluation of the prognostic factors revealed an association between the GG genotype at position -670 and liver involvement in ALL patients (p < 0.04). Although patients with -1377 AA genotype showed shorter mean complete remission duration, the result of survival analysis did not reach to be significant. In conclusion, results of this study showed no contribution of Fas genotypes at positions -670 and -1377 to risk of ALL in children. The association of Fas GG genotype at position -670 with liver involvement in the patients may show its important role in prognosis of ALL.