Purpose <p>Despite improved surgical and medical therapies, it remains a disease entity that is difficult to cure chronic rhinosinusitis with nasal polyps (CRSwNP), given a recently-reported incidence up to 4% of the population severely affects patients’ quality of life. In this retrospective study, we attempted to assess the role of another important inflammatory cell, the blood basophil, in a large series of patients with CRSwNP (<i>n</i> = 316) across three different age groups.</p> Methods <p>The investigation concerned 316 consecutive patients undergoing endoscopic sinus surgery (ESS) for CRSwNP. We divided these patients into three groups according to age, of which, 46 consecutive geriatric patients ( ≧ 61y), 243 consecutive young adult CRSwNP patients (19-60y), and 27 pediatric patients (≤ 18y) were enrolled.</p> Results <p>Compared between groups, WBC and eosinophil counts in peripheral blood were not statistically different among the three groups, while blood basophil (<i>p</i> = 0.016), lymphocyte (<i>p</i> &lt; 0.001), monocyte (<i>p</i> = 0.031) counts and LM scores (<i>p</i> = 0.025) were statistically different between groups, all of which were significantly different between pediatric and adult groups, pediatric and elderly groups. Spearman correlation analysis revealed blood basophil counts were positively correlated with blood eosinophils, leukocytes, lymphocytes, monocyte counts, and LM scores overall in the sample as a whole (<i>p</i> &lt; 0.001).</p> Conclusion <p>The heterogeneous role of blood basophils identified in different age sub-cohorts of CRSwNP supports the hypothesis that blood basophil count may reflect the severity of inflammation in CRSwNP patients. In addition, we should pay attention to the long-term follow-up of pediatric patients with CRSwNP.</p>