Methylenetetrahydrofolate reductase (MTHFR) is one of the most critical enzyme in folic acid metabolism, and it converts 5,10-MTHF to 5-MTHF. 5,10-MTHF is required for conversion of uridilate to thymidylate. On the other side, MTHFR enzyme causes methylation of homocysteine into methionine, leading to methylation of DNA. Chemotherapeutic agents have different effects, but DNA is the target for most of them. Because folate is the cornerstone in DNA synthesis, we analysed herein if the polymorphisms in MTHFR gene can alter the susceptibility of lymphoproliferative disease risk and if it has an effect on chemotherapy response. One hundred fifty-six patients with lymphoid malignancies and 82 healthy controls were included into the study. Neither gene frequencies nor allel frequencies were found to increase lymphoproliferative disease risk significantly in both overall group and subgroups. Although it was not statistically significant, we found a 2.7-fold increased risk in acute lymphocytic leukaemia (ALL)/Burkitt lymphoma patients with TT genotype [odds ratio (OR), 2.7; 95% confidence interval (CI), 0.88-8.2] than CC genotype but a 1.7-fold decreased risk with TT genotype in diffuse large B-cell lymphoma (DLBCL; OR, 0.58; 95% CI, 0.17-1.88) and a 1.8-fold decreased risk in Hodgkin's lymphoma with TT genotype (OR, 0.55; 95% CI, 0.10-2.87) than CC genotype. The chemotherapy response was analysed in DLBCL, Hodgkin's lymphoma and ALL/Burkitt's lymphoma because these patients received standard chemotherapy protocols. No significant difference was detected between responder and non-responders according to MTHFR T677C polymorphism, but the patients who had TT genotype respond 1.75-fold worse than CC (OR, 0.57; 95% CI, 0.07-4.64) in ALL patients (p=0.59), and in DLBCL, CT genotype revealed a 1.8-fold worse response than CC genotype (OR, 0.54; 95% CI, 0.17-1.7), but TT genotype revealed 2.6-fold better response rates than patients with CC genotype (OR, 2.6; 95% CI, 0.26-26.8). As a conclusion, MTHFR C677T polymorphism does not increase the risk of lymphoproliferative disease, and it does not have an effect on chemotherapy response significantly; however, the patients with TT genotype have a slightly increased risk for ALL, and they also respond worse than CC genotype. TT genotype slightly decreases the risk of DLBCL, and the patients have much favorable response rates.