The present study investigates the association between IL12Bpro and +16974A/C in 3' -untranslated region (UTR) polymorphisms of IL12B and IL-12p40 serum level related to development of colorectal cancer (CRC). Our results showed similar distribution of both the investigated polymorphisms among CRC patients and healthy donors, which suggests that these polymorphisms in IL12B were not associated with the development of CRC. However, we found an increased IL-12p40 level in sera from patients compared to healthy donors and the highest level was observed in stage I compared to more advanced stages of CRC. These findings demonstrated that IL-12p40 serum level has an association with the progression of CRC.