Objective We explored the role of insulin-like growth factor 1 (IGF-1) in the development of lung cancer. Methods We used immunohistochemistry to measure the expression of IGF-1 and IGF-1 receptor (IGF-1R) in specimens of tissue and perioperative circulation from 80 patients with primary non-small-cell lung cancer (NSCLC) and from 45 patients with benign pulmonary lesions (BPLS). Correlations of those measurements with clinicopathologic characteristics and clinical follow-up were analyzed. Circulating IGF-1 was measured before and after surgery in all patients. Results Compared with BPL specimens, NSCLC specimens showed overexpression of IGF-1and IGF-1R (p < 0.001). The expression levels of IGF-1 and IGF-1R were significantly associated with advanced-stage disease (p = 0.034 and 0.029 respectively) and lymph node metastasis (p = 0.012 and 0.017 respectively), and expression of IGF-1 correlated with tumour differentiation and tumour diameter (p = 0.011 and 0.021 respectively). Specimens positive for IGF-1 or IGF-1R were significantly correlated with shorter patient survival (p = 0.0012 and 0.0016 respectively). After surgery, circulating IGF-1 was significantly elevated in patients with BPL (p = 0.0346) and significantly lower in patients with NSCLC (p = 0.0030), especially in those with advanced-stage disease, a larger tumour size, regional lymphoid node metastasis, or lesser differentiation (p = 0.0092, 0.0051, 0.0131, and p < 0.001 respectively). Conclusions In NSCLC, IGF-1 and IGF-1R are upregulated, and expression of those factors is correlated with tumour progression and prognosis in NSCLC patients. Radical resection of NSCLC can directly influence the serum concentration of IGF-1. Autocrine/paracrine IGF-1 might be playing an important role in the development of lung cancer.