Objective To analyze clinical features and prognosis of primary intestinal T cell lymphoma (ITCL) which was misdiagnosed as Crohn's disease (CD), and summarized the key points of differentiation between ITCL and CD. Methods From January 2003 to January 2014, clinical data of patients with ITCL once misdiagnosed as CD were retrospectively analyzed, which included demographic, clinical, pathological and prognostic data. The data of 177 patients diagnosed as CD from January 2012 to January 2014 were collected. The demographic, clinical, pathological and prognostic data of these two groups were analyzed and compared. The continuous variables were compared with t test or Mann-Whitney U test, and the differences of classification variables between two groups were analyzed by Chi-square test or Fisher exact probability method. Results A total of 18 patients (17 males and one female) with ITCL misdiagnosed as CD were enrolled in the study, and the median age at diagnosis was 38.5 (28.8 to 42.5) years and the median duration of diagnosis was 6.00 (3.75 to 13.25) months. The common primary symptoms were abdominal pain (12/18), diarrhea (13/18) and anemia (13/18). Intestinal perforation was primary symptom in two cases (2/18). However, B symptoms of lymphoma was observed in 16 patients, which included fever in 13 patients, weight loss in 16 patients and night sweat in one patient. One or more serious complications appeared in 12 patients, which included intestinal perforation in nine patients, severe gastrointestinal bleeding in seven patients and intestinal obstruction in two patients. In 177 patients with CD, 104 patients were male (58.8%), and the median age at diagnosis was 22.0 (18.0 to 29.0) years. The primary symptoms were abdominal pain (88.7%, 157/177), diarrhea (55.9%, 99/177), anemia (63.8%, 113/177), fever (33.3%, 59/177) and weight loss (59.9%, 106/177). During the disease course, 30 patients (16.9%) had intestinal perforation (mainly chronic), 12 patients (6.8%) had intestinal obstruction and seven patients (4.0%) had severe gastrointestinal bleeding. Compared to CD patients, male patients were more common in ITCL (χ2=8.837, P<0.01), age at diagnosis was older (χ2=314.5, P<0.01), the disease course was shorter (U=385.0, P<0.01), weight loss (χ2=5.867, P<0.05) and fever (χ2=10.609, P<0.01) were more common in clinical symptoms and intestinal perforation and severe gastrointestinal bleeding were more common in complications (χ2=9.185, 24.908, both P <0.01). The lesions of ITCL were multiple lesions, small bowel involved in eight cases, colon involved in 14 cases and one case with esophagus involved. Under endoscopy examination, most lesions appeared as ulcerations and were segmentally distributed. Compared to CD, lymphocyte proliferation was more common in the intestinal histopathological findings of ITCL (17/18 vs 19.7%(35/177); χ2=42.844, P<0.01) and granuloma was rare (0 vs 42.8%(76/177), χ2=12.665, P<0.01). Among 18 patients with ITCL, nine received chemotherapy and the median survival time was two months. Conclusions Primary ITCL had non-specific symptoms and was easily misdiagnosed as CD. More attention should be paid to the differential diagnosis of the two disease. Key words: Primary intestinal T-cell lymphoma; Crohn disease; Clinical features