According to the good genes hypothesis and energy allocation theory, human adult body height may reflect biological quality. An important aspect of this quality is immune system functioning (ISF). The aim of this study was to evaluate the relationship between ISF and body height in healthy people. The ISF was determined by several important innate (total complement and lysozyme activity, neutrophils function) and adaptive immune parameters (lymphocytes, IgA and IgG, and response to flu vaccine). Overall, 96 males and 97 females were subjected to flu vaccination, and of these 35 males and 34 females were subjected to tetanus. Blood samples were collected before and 4 weeks after vaccination. Immunomodulatory factors: participant's age, body fat and free testosterone levels, were controlled. There was no association between body height and all analysed immune parameters for both sexes. That might suggest that in western society, a women’s preference for taller men is not related to “good genes for immune competence”. We propose the novel Immunity Priority Hypothesis that explains the lack of relationship between adult body stature and ISF. This hypothesis, however, does not contradict the signalling role of a man's body height as a morphological marker of biological quality.