© 2019 The Royal College of RadiologistsAIM: To present cross-sectional imaging, surgical findings, and follow-up results of diaphragmatic mesothelial cysts. MATERIALS AND METHODS: Radiological findings for location, size, shape, and internal structure of cysts were reviewed retrospectively. For patients that underwent surgery, surgical reports and laparoscopy images were reviewed. In conservatively managed patients, changes in size and imaging findings of the cyst were assessed during follow-up visits. RESULTS: A total of 13 paediatric cases with an imaging and/or pathological diagnosis of diaphragmatic mesothelial cyst were identified. In all cases, the cystic lesions were located between the diaphragm and the posterolateral aspect of the right lobe of the liver. Eleven lesions (84.6%) had a bi-lobulate shape. Eight of these cases underwent laparoscopic cyst aspiration/unroofing. The postoperative course was uneventful and there were no cases of recurrence. The remaining five cases were managed conservatively with follow-up available in four cases. In three cases (75%), there was reduction in the size of the cysts with a mean volume reduction of 55%. CONCLUSION: Diaphragmatic mesothelial cysts are congenital cystic lesions that are usually detected incidentally. A common pitfall is incorrect interpretation of the lesion as a hepatic cyst. Conservative management with imaging follow-up can be adopted in asymptomatic cases with typical imaging findings.