Objective To investigate the effects of L-glutamine-supplemented parenteral nutritional sup- port on nutritional status, immunity, and inflammatory response in patients with lung cancer following radical opera- tion. Methods Forty-two malnourished patients with lung malignancies who had undergone radical operations were randomly divided into PN plus group (n =22) and PN group (n = 20). From day 1 to day 5 after operations, parenteral nutrients with the non-proteinic calorfic value of 90 kJ · kg-1 d-1 and nitrogen 0.25 g · kg-1 d-1 were given. From day 2, liquid diets were provided to both groups, and L-glutamine particles (30 g) were provided to PN plus group. Peripheral blood specimens were collected before operation, on day 1, and on day 7 after the oper- ations to determine the serum levels of albumin, prealbumin, transferrin, T lymphocyte subgroup 3 (CD3), CD4, CD8, CD4/CD8, immunoglobulin A (IgA), IgG, IgM, and C-reactive protein. Results The levels of the serum transferrin [(2.29±0.34) vs. (2.15±0.42) g/L], prealbumin [ (0. 27±0.76) vs. (0.23±0. 84) g/L], CD4 (30.9%±2.2% vs. 28.9%±2. 3% ), CD4/CD8 (1.17±0.19 vs. 1.10±0. 81), IgG [(12. 94 2.08) vs. (11. 19±1. 95) g/L] were all significantly higher in the PN plus group than those in PN group on day 7 (P <0. 05) . The level of serum C-reactive protein was significantly lower in PN plus group than that in PN group on day 7 [(31.6±16.7) vs. (36.5±13.3) mg/L, P<0.05]. Conclusion Postoperative L-glutamine-supplemented parenteral nutrition support can improve the nutritional status and immune function and reduce the acute inflammatory response in patients with lung cancer.