The paper describes a case of twin pregnancy with complete hydatidiform mole (CHM). According to the data available in the literature, the concurrence of CHM with a normal placenta and a viable fetus occurs in 1 per 20,000—100,000 pregnancies, requires a differential diagnosis with partial hydatidiform mole and placental mesenchymal dysplasia, and is characterized by a high rate of complications. In this concurrence, the frequency of persistent trophoblastic disease is as high as 50%. In this case, the pregnancy ended in a spontaneous abortion at 16—17 weeks of pregnancy. A morphological examination determined the fetus without congenital malformations with normal placental weight and structure and the adjacent intact placental tissue with the macro- and microscopic signs of CHM. The diagnosis was confirmed by the lack of р57 expression in the villous trophoblast and stroma in the tissue of the hydatidiform mole. The patient was diagnosed with persistent trophoblastic disease at 2 months after the abortion,