Purpose: Although chronic and recurrent rhinosinusitis is prevalent in children, little is known about its causes. Here, we investigated the humoral immunity in children with chronic or recurrent rhinosinusitis. Methods: We examined 16 children attending the outpatient clinic at the CHA Bundang Medical Center including 11 boys and 5 girls, aged 3-11 years (mean age, 5.6 years), who had rhinosinusitis for >3 months or >3 times per year. The complete blood count with differential and total serum concentrations of Immunoglobulin (Ig) E, IgA, IgD, IgM, IgG, and IgG subclasses ($IgG_1$, $IgG_2$, $IgG_3$, and $IgG_4$) of all children were measured. All subjects received 23-polysaccharide pneumococcal vaccination (PPV), and the levels of antibodies to 5 serologic types (4, 6B, 14, 18C, and 23F) of pneumococcal capsular polysaccharide antigens were measured before and after vaccination. Post-PPV antibody titers ${geq}0.35{mu}g/mL$ or with a ${geq}4$-fold increase were considered as positive responses. Results: The titers of IgG, IgA, IgD, and IgM were within normal range in all 16 children, whereas the total IgE concentration was higher than normal in 2 children. $IgG_1$ deficiency was observed in 1 patient and $IgG_3$ deficiency in 3. After PPV, 1 patient failed to respond to all 5 serologic types, 2 failed to respond to 4 serologic types, and 2 failed to respond to 3 serologic types. Conclusion: Clinicians should consider the evaluation of humoral immune functions in children with chronic or recurrent rhinosinusitis who do not respond to prolonged antibiotic treatment.