BACKGROUND Advanced non-small cell lung cancer has poor prognosis and low survival. Immunotherapy with the use of immune checkpoint inhibitors is a relatively new method of treatment that offers a chance to significantly extend the survival and quality of life of patients over that obtained with conventional chemotherapy. One of the complications of immunotherapy is immune checkpoint inhibitor-related pneumonitis. CASE REPORT We analyzed the available medical data on the treatment of 22 patients with non-small cell lung cancer who were treated in our clinic and qualified for immunotherapy with one of the anti-PD-1/anti-PD-L1 agents: nivolumab, atezolizumab, or pembrolizumab. In this group of patients treated with immune checkpoint inhibitors, 4 patients experienced immune checkpoint inhibitor-related pneumonitis. CONCLUSIONS Immune checkpoint inhibitor-related pneumonitis is a rare but potentially life-threatening complication of immune therapy. It can manifest in many ways, from asymptomatic to severe cases, which require quick action and treatment. Knowing the spectrum of symptoms and being alert to the possibility of such a complication is an important skill for doctors who use immunotherapy in their patients.