Placental lesions, including placental infarction, are associated with fetal and neonatal mortality and morbidity. We present a case of fetal growth restriction associated with an old, diffuse placental infarction. Because the placenta had only a single viable cotyledon, the others being atrophic, the lesion appeared to be a placental tumor on prenatal ultrasonography. The patient did not have pregnancyinduced hypertension. At 31 weeks of gestation, a cesarean delivery was performed because of fetal growth arrest and breech presentation. A small-for-gestational age infant was delivered with Apgar scores of 8 at both 1 and 5 minutes, and the infant had cleft palate and cleft lips. Pathological examination of the placenta revealed an old, diffuse infarction without neoplastic change. In cases in which a placental tumor causing fetal growth restriction is strongly suspected, diffuse placental infarction should be considered as part of the differential diagnosis, because placental tumors are associated with poor maternal prognosis. (J Nippon Med Sch 2015; 82: 156 158)