Objective To analyze the misdiagnosis in extraovarian peritoneal carcinoma(EOPC). Methods The clinical manifestation, blood tumor marker, imaging examination, laparotomy, pathology, treatment and prognosis of 19 EOPC patients were retrospectively analyzed. Results The clinical symptoms were abdominal distention, abdominal pain and swelling. 17 cases were tested for blood CA-125 with 15 at abnormaly high level, and in 4 cases ascites was CA-125 positive ( ＞ 10 KU/L). Tumor cells were detected in the ascites in 12 cases. Three cases were misdiagnosed as of uterine origin, 13 cases misdiagnosed as adnexal tumor, 1 case was misdiagnosed as bladder and intestinal tumor. Only 2 cases were correctly diagnosed before the operation. All of the cases were pathologically proved as peritoneal carcinoma. The five-year survival rate was only 20 percent. Conclusions Abdominal distention and pain with unknown causes were the primary manifestations of EOPC, elaborate physical examination sometimes may provide with important information. The significant elevation of serum CA-125 and the ascites cytology may be helpul for the differential diagnosis of PPC. CT scan is valuable for the diagnosis of EOPC.