The CHEK2 gene encodes the CHK2 protein, which is kinase involved in DNA repair processes. By activating a lot of cell substrates, it can regulate the cell cycle, demonstrates suppressive effects, and participates in the senescence and apoptosis processes. Mutations in the CHEK2 gene are associated with increased risk of numerous cancers. The case described herein is that of a woman with a missense mutation that results in the substitution of isoleucine for threonine at position 157. This variant of the mutation doubles the risk of papillary thyroid carcinoma two times and causes up to 9% of these cancer. It is also associated with a two-fold increased risk of cancers of the kidney (10%), colon (10%), and ovary (10% - G1), a 1.6-fold increased risk of prostate cancer (8% of all of them and 12% of familiar ones), and a 1.5-fold increased risk of breast cancer (7%). The screening procedures were initiated in a carrier who revealed papillary thyroid carcinoma. Genetic screening of the family diagnosed her daughter as the carrier of this mutation. Until now no active cancer disease has been recognized in the daughter. On the example of the presented case we discuss indications for screening in cases of positive family history. The group especially predisposed seem to be patients with at least two coexisting carcinomas. Having diagnosed the mutation, it is necessary to do genetic screening of family members. Continuous oncological observation of the carriers of CHEK 2 mutation is essential.