The calcaneus is an uncommon site for unicameral bone cysts. Little is known about the etiology of these lesions. Such cysts are usually symptomatic, because of the concentration of forces through the heel and require surgical treatment in most of the cases. Material and methods. The purpose of this paper is to present a case of a 25-year-old athlete who was admitted to the Department of Microsurgery and Reconstructive Surgery with pain in the region of the right calcaneus during walking, which appeared 2 months ago. The patient underwent plain chest X-ray, general blood and urine test, all of them came normal beside the X-ray of the foot which showed a 4,0x2,0x2.0 cm cystic lesion of the right calcaneus. The patient underwent surgical treatment, which consisted of extended curettage of the cyst followed by filling of the bone defect with 10 cm3 demineralized allogeneic bone paste mixed with 10 ml of patient blood. The demineralized allogeneic bone paste was prepared by the Human Tissue Bank. An intraoperative Xray was performed and showed that the bone defect was filled with demineralized allogeneic bone paste. There were no early or late postoperative complications encountered. The patient was discharged from the hospital the second day after the operation. Conclusions. Imaging data are required when a cystic mass is suspected. Surgical treatment in combination with using of demineralized bone paste should be considered as an effective treatment for bone cysts. Further evaluation is required.