Background: To determine the imprinting status of the IGF2 in Chinese patients with primary lung cancer and to analyze the clinical significance of the loss of imprinting (LOI) of IGF2. Materials and Methods: PCR-RFLP and RT-PCR-RFLP were carried out to select heterozygous cases for the ApaI polymorphism within exon 9 of the IGF2 gene and further analyze IGF2 LOI in 64 lung cancer patients, respectively. Results: Of 64 lung cancer patients, 31 were heterozygous for IGF2. The positive rates of IGF2 LOI of lung cancer foci, matched paracancer tissues, and normal lung tissues were 77.4% (24/31), 61.3% (19/31), and 29.0% (9/31), respectively. The LOI differences for IGF2 among the three groups were statistically significant (chi(2)= 15.267, p= 0.000), and the LOI frequency of IGF2 in normal lung tissue was significantly lower than that in lung cancer foci and paracancer tissues (chi(2)= 14.577, p= 0.000; chi(2)= 6.513, p= 0.011). No statistical difference was observed between the lung tumor group and the matched paracancer group (chi(2)= 1.897, p= 0.168). The prevalence of advanced clinical stages (chi(2)= 2.379; p= 0.017) and lymph node metastasis (chi(2)= 5.552; p= 0.018) was significantly higher for LOI-positive paracancer tissues than for LOI-negative paracancer tissues. Conclusions: IGF2 LOI is highly frequent in Chinese primary lung cancer patients, especially those with increased risk of lymph node metastasis and advanced clinical stages. IGF2 LOI may be an early epigenetic event in human lung carcinogenesis.