Introduction. Li-Fraumeni syndrome (LFS) is a very rare familial disease with the predisposition to the development of malignant tumors, such as osteosarcoma, breast cancer, brain neoplasm, leukemia, and adrenal tumors. Inheritance is autosomal dominant and is caused by heterozygous mutations in the p53 gene. The diagnosis is based on clinical criteria: a person under the age of 45 years suffering from sarcoma, the closest relative younger than 45 years diagnosed with cancer and a relative of the first or second degree, which is up to 45 years, was diagnosed with cancer and was diagnosed with sarcoma at any age. Case report. The presented family with three members diagnosed with malignant disease typical for LFS suggests the need to carefully follow those diagnosed with LFS related tumor. A 24-yearold man diagnosed and treated for osteosarcoma of the maxilla died in the first year. His younger brother was submitted to surgery due to osteosarcoma of the mandible three years later, and a year later in his 24 year he had no signs of locoregional recurrence. Their mother was operated in 1996 for glioblastoma multiform brain cancer and ductal carcinoma, and died two years later at the age of 33. Conclusion. The presented family highlights the need for careful examination, inspection and notification of the risks of family members diagnosed with LFS related tumors.