Background: Despite the presence of robust evidence, there is very limited data on the efficacy of allergen immunotherapy (AIT) for selected patients. Accordingly, we aimed to evaluate the efficacy and perceived satisfaction of a 3-year course of sublingual immunotherapy (SLIT) in a paediatric population with allergic rhinitis and/or asthma., Methods: A pilot, monocentre, retrospective cohort study was performed. One hundred fifty-three children who fulfilled the criteria for allergic rhinitis and asthma and were either mono- or poly-sensitized were enrolled. A standardized questionnaire assessing perceived efficacy, use of rescue medication, disease control, number of exacerbations, quality of life, and perceived satisfaction was administered to each patient., Results: Seventy patients (49 males, 21 females; mean age, 14.3±1.9 years) were included in the final analysis. All 70 patients received SLIT for up to 3 years, with 100% adherence to the treatment throughout the study. Significant improvements in symptoms and quality of life were reported (p<0.01). There was also a significant decrease in disease severity, use of rescue medication, and sleep disturbances (p<0.01). Additionally, a significant improvement in school performance was also recorded (p<0.01). Of the enrolled patients, 60 out of 70 (85.7%) reported being very satisfied, 6 out of 70 (8.57%) were much satisfied, and 4 out of 60 (5.71%) were satisfied., Conclusions: We were the first to demonstrate the efficacy and perceived satisfaction of a 3-year SLIT in a paediatric population, with 100% treatment adherence throughout the study., Competing Interests: EC and FF work in Lofarma. The remaining authors declare no conflict of interest.