The aim of the study was to assess the expression and significance of HER2 and HER3, and Ile/Val single nucleotide polymorphism (SNP) of HER2 in lung cancer patients. Thirty seven cases of lung cancer were investigated immunohistochemically for HER2 and HER3 expression. PCR followed by restriction fragment length polymorphism (RFLP) was used to analyze the presence of HER-2 SNP at codon 655 in 20 samples. The results were compared with clinical and pathological parameters of investigated patients.We found that 100% of the cases were negative for HER2, 29.7% were with moderate or strong HER3 expression and 70.3% of the tumors-without or with low expression for HER3. Lymph node metastasis were found in 40% of HER3 positive cases (χ(2) = 4.752; p = 0.029). Moderately-differentiated tumors do not express neither of investigated markers (χ(2) = 6.719; p = 0.035). HER2 RFLP-PCR analysis showed genotype AG in five patients (25%) and the rest of 15 cases (75%) had АА (Ile/Ile) genotype. Patients with metastasis had genotype АА (Ile/Ile) in 80% and genotype AG (Ile/Val) in 20% (χ(2) = 2.857; p = 0.091).Our results indicate that SNP in HER2 codon 655 and investigation of HER2 and HER3 expression could be helpful to outline the prognosis for patients with lung adenocarcinoma.