ObjectiveTo evaluate the role of CD3+CD4+T cells in patients with nosocomial infection in ICU. MethodsOne-hundred and eleven patients who admitted in ICU and in respiratory department from March to December in 2014 were recruited in the study.There were 33 patients with community-acquired pneumonia (CAP group), 31 patients without nosocomial infection (NNI group), and 47 patients with hospital-acquired pneumonia (HAP group).The counts of T cells, B cells, CD3+CD4+ T cells, CD3+CD8+ T cells, and NK cells were compared among three groups. ResultsThe comparison among the groups had no statistical significance in sex and age(P > 0.05).The three groups had statistical significance in APACHEⅡscore, CD3+CD4+T cells, T cells and B cells, but had no statistical significance in CD3+CD8+T cells, CD3+CD4+/CD3+CD8+ T cells, NK cells, white blood cells, neutrophils, procalcitonin or C reactive protein.CD3+CD4+T cells of HAP group were less than other two groups.The area under the ROC curve (AUC) was 0.660, with a threshold of 29.96%, a sensitivity of 93.8%, and a specificity of 40.4%. ConclusionCD3+CD4+ T cell is an independent predictor for nosocomial infection.