A retrospective analysis of medical data of 157 children, suspected for pertussis, aged from 1 month to 17 years, hospitalised in Paediatric, Nephrology and Allergology Clinic, Military Institute of Medicine from January 2009 to March 2013 was undertaken. Information concerning age, sex, duration of cough, presented symptoms and laboratory tests results were analysed. Statistical analysis was performed using standard statistical software (Statistica PL). The significance level was set as p<0.05. Pertussis, as a reason of cough, was found in 31 cases. Statistical analysis showed no significant differences between patients with acute and chronic cough, as far as a frequency of pertussis infection is concerned. Gender was not associated with the pertussis infection (p>0.05). Occurrence of cough and apnea was strongly associated with positive pertussis serologic laboratory tests. The statistical significance between low amount of white blood cells and low Biernacki’s test rate and positive pertussis serologic laboratory tests was found. This finding does not fit to a classical course of disease. The reason of this discrepancy may be a fact, that in analyzed group only two children were not vaccinated (under the age of 2 months). The classical course of disease is observed only among unvaccinated patients. Among children diagnosed due to recurrent respiratory tract infections 8.3% had positive pertussis serologic laboratory tests.