Influenza is an acute viral respiratory disease, which is particularly common in the paediatric population. Every year it affects about 25% of children. According to the National Institute of Public Health – National Institute of Hygiene, almost three times as many cases of influenza were registered in the 2022/2023 infectious season compared to previous years. However, in the era of the influenza epidemic, diagnostic vigilance should be maintained, keeping in mind that the symptoms of some serious bacterial infections may initially mimic those of influenza. We present a case report of a 3-year-old boy with influenzalike symptoms, who was finally diagnosed with lobar pneumonia complicated by parapneumonic effusion. Early diagnosis and treatment spared the patient from invasive treatment for complications of pneumonia.