Immunological mechanisms involved in the genesis of the immune response against viral infections take into account the activation of both innate adaptative response. Innate immune defenses trigger a rapid local response, which is often sufficient to control viral infection, and promotes the subsequent activation of specific immune defenses. Natural killer (NK) cells that constitute a subpopulation of lymphocyte-related cells are a key factor of innate immune response and play a role in defense against viral infections by killing infected cells or by producing cytokines and interacting with adaptative immune system's cells. Killer immunoglobulin-like receptors (KIRs) regulate the activation of NK cells through their interaction with human leukocyte antigens (HLA). KIRs and HLA loci are highly polymorphic and certain HLA-KIRs combinations have been found to protect against viral infections. In this study we review how the KIRs/HLA repertoire may influence the course of hepatitis B virus (HBV), hepatitis C virus (HCV), cytomegalovirus (CMV) and Herpes Simplex Virus 1 (HSV-1) infection. Results of our study suggest that a combination of KIRs/HLA gene/alleles is able to predict the outcome of viral infection and allows to plan successful customized therapeutic strategies.