Head and neck tumors are a group of malignancies originating from the stratified squamous epithelium and affecting the upper aerodigestive tract. They are in the top ten most common cancers, and their incidence is increasing due to the prevalence and frequency of risk factors that promote their occurrence. Traditionally, the primary treatment modality for this group of tumors was surgery with adjuvant radiotherapy, i.e. primary radiotherapy; however, both methods led to a high degree of mutilation and reduced quality of life for patients, especially in the case of locally advanced and metastatic tumors. With the progress of immunology, it was discovered that tumors in general, and head and neck tumors in particular, are very immunologically active tissues, with an extensive response of the immune system to the presence of tumor cells. Based on this, a new therapeutic modality was developed with the aim of acting on immune cells in the tumor microenvironment - immunotherapy. The type of immunotherapy in clinical use in the treatment of head and neck tumors are immune checkpoint inhibitors, specifically inhibitors of the PD-1 (programmed death 1) signaling pathway. This paper presents an overview of tumor immunity as a basis for immunotherapy, and the specificities of the extremely immunologically active tumor microenvironment in head and neck tumors, on the basis of which the clinical application of immunotherapy in the treatment of these malignant diseases began. The issue of immunotherapy itself as a new and often still experimental therapeutic modality is elaborated; all its forms are mentioned, with special emphasis on PD-1 inhibitor therapy, which is used in head and neck tumors. Adverse events related to the use of PD-1 inhibitors, primarily adverse effects or side effects, as well as the development of resistance are also listed. Of the adverse effects, the most significant are those specific to immunotherapy; although relatively rare, they can cause serious and long-term health problems. The development of resistance represents one of the biggest problems of treatment with immunologically active compounds; the possible causes of this phenomenon are numerous, and can be found both in the nature of the tumor tissue and in the physiology of the patients themselves. In order to overcome the mentioned shortcomings of the use of immunotherapy, combinations with other therapeutic modalities common for the treatment of malignant diseases are extensively researched; some of them are already being implemented, while others are only in the early stages of testing.