The natural history of oncogenic human papillomavirus (HPV) infections results from interactions of the virus, the host, and multiple cofactors. We studied the association between humoral immune response to HPV and smoking in 191 HPV infected women prospectively. Two follow-up samples (first and last) were analysed for serum cotinine levels, IgA and IgG antibodies to HPV16 and 18, and Chlamydia trachomatis using ELISA methods. HPV DNA analyses were also performed, and HPV16/18 antibodies were detectable in 23 of 40 (57.5%) HPV DNA-positive women. We performed age-stratified analyses and found that young smokers were less likely to develop HPV16/18 antibodies than non-smokers (OR: 0.2, 95% CI 0.0-0.9). Furthermore, they had a significantly decreased tendency of maintaining constant HPV16/18 IgG antibody positivity by the end of the follow-up (OR: 0.1, 95% CI 0.0-0.8). Smoking did not affect the development of HPV antibody responses in women over 30 y of age. Our results suggest that smoking may induce impaired antibody response in HPV16/18-infected young women.