Sublingual immunotherapy (SLIT) is an at-home, self-administered, long-term therapy. As with other chronic diseases, patient adherence is a prerequisite for the success of SLIT. Its ease of intake and convenience should ensure adequate patient compliance; however, a recent post-marketing manufacturers’ survey has shown a very high rate of discontinuation. The available literature on patient adherence to SLIT is reviewed in the present article. Great differences exist between controlled studies, which show a satisfactory adherence rate, and long-term real-life studies, which show poor compliance with SLIT. Remarkable divergence in the weight placed on different reasons for SLIT discontinuation is reported in the various studies. The main reasons for withdrawal are analysed and discussed. Data from placebo-controlled studies demonstrate that adherence depends less on the patient's perception of the inefficacy of therapy or other causes than on the patient's motivation, that is the patient's decision to participate in the trial and to meet the researcher's expectations. The enrolment of patients who agree to enter a blind, placebo-controlled trial is conceptually similar to a concordance process. Concordance is a consultation process that aims to establish a therapeutic alliance between the physician and patient and to bring about agreement on a therapeutic programme. Concordance is based on the patient's beliefs and needs and implies actions that support the patient's adherence. Suggestions are given for a SLIT management strategy based on the concordance process and designed to integrate the patient's viewpoints into treatment-related decisions and to meet patients’ preferences and their health-system-related needs.