Objective: To assess the incidence of the sacroiliac joint vacuum phenomenon (SIJ VP) in paediatric patients and the relationship between the presence of VP and clinical factors such as age, sex and body mass index (BMI). Methods: We retrospectively reviewed clinical data and imaging findings of 60 patients who underwent abdominopelvic CT (AP CT) between January and June 2015. Patients were divided into VP group and non-VP group based on the presence/absence of VP, and the groups were compared. In addition, other degenerative changes in the SIJ were recorded. Results: The SIJ VP was detected in 19 (31.6%) patients. There were no significant differences in sex distribution between VP and non-VP groups (p50.781). The age of the VP group was significantly higher than that of the non-VP group (p,0.001). After adjusting the BMI for age, there was no significant association between high BMI and the presence of SIJ VP (p50.326). Other degenerative changes were not noted in any of the patients. Conclusion: The SIJ VP is not an uncommon finding in paediatric patients. The prevalence of SIJ VP in paediatric patients is similar to its prevalence in adults. The SIJ VP is related to patient age, but not to sex or BMI in children and young adolescents.