Due to the growing prevalence of cervical cancer and turning it into a national health problem in developing countries, the best screening method is always considered. Herein we are going to report three cases of false negative tests of pap smear test, which is the main screening method in Iran. Our patients were 31,35 and 37 years old respectively, who did not have any evidences in favor of precancerous cervical lesions in regular screening by pap smear test but eventually were diagnosed as locally invasive squamous cell carcinoma of the cervix. Two of them had out-of-wedlock sex, and one, was heavy smoker on their past history. Although pap test has a good accuracy for differentiation between normal and abnormal cervical cells, but in false negative cases, because of delay in early diagnosis can leads to advanced stages of cervical cancer and poor outcomes. Therefore, it may be better to use complementary methods for screening in high-risk individuals.