Aims: To study the clinical and radiological result of arthroreisis with Giannini’s endo-orthotic implant in the treatment of paediatric flat-foot. Methods: 65 cases were studied in 37 patients, 60% were males and 40% females. The follow-up was 26.5 months. The total average age was 9.4, range of 5 and 14 years old. Surgery in patients that had suffered fractures, inflammatory, rheumatic or neurological processes was contraindicated. We studied: pain, functional and sport activity, as well as the development of radiographic measurements at 3, 6 and every 12 months after the operation. Results: Pain improved from preoperative 60% to postoperative 6.2%. The percentage of postoperative footprint was normal in 58.5% of the cases and first degree flatfoot in 41.5%. Postoperative sport activities were taken up by 49.2% of the patients. The 8 mm endoorhotic implant was the most used (66%). We performed Achilles tenotomy in 58.5% of the cases. The radiographic angles whose correction was greater with regard to the preoperative angle were: talar- first metatarsal (96%) and calcaneal- pitch (34%). Postoperatively the endo-orthotic implant-talus angle had an influence on the rest of the radiographic measurements. There was no postoperative deterioration in any of the radiographic angles measured in the monitoring period. Complications: we had 10.7%, with postoperative pain as a most frequent (6.2%). There was no infection or local reaction to a foreign body. We did not remove the endoorthotic implant systematically. Conclusions: 1) Footprint became normal in over half the cases; 2) radiological morphology was corrected 2/3 of the cases and it did not alter throught follow-up; 3) surgical technique respect anatomical structure of the foot, without medial surgical time.