Background/Aims: Among colorectal neoplasms, laterally spreading tumors(LSTs) are defined as tumors over 10mm in diameter that are low in height and grow superficially. We performed this study to analyze the clinicopathologic characteristics of LSTs in colorectum. Materials/Methods : Forty six LSTs diagnosed by colonoscopy were analyzed according to their endoscopic and pathologic findings. The lesions were macroscopically classified into two categories according to their surface structure; granular type(G type), nongranular type(F type). Granular types were subdivided into granular-homogeneous type(GH type) and mixed-nodular type(MN type). Results : 1) Incidence of LSTs were 46(2.0%) among the total 2276 colorectal adenomas. 2) Out of 46 LSTs, 22 (47.8%) were less than 20mm in diameter, 20 (43.5%) were 20-30mm in diameter, 4 (8.7%) were larger than 30mm in diameter. 2) The most frequent location was the rectosigmoid colon(54.3%, 25/46), followed by the ascending colon(21.7%, 10/46). 4) GH types were 37.0%(17/46), MN types were 30.4%(14/46), F types were 32.6%(15/46). 5) Histopathologically, adenoma components were tubular types in 65.2%(30/46), tubulovillous types in 26.1%(12/46), villous types in 8.7%(4/46). 6) High grade dysplasia, mucosal carcinoma and submucosal carcinoma were present in 19.6%(9/46), 13.0%(6/46), 6.5%(3/46), respectively. The overall malignancy rate was 19.6%(9/46). 7) Malignancy rates according to their sizes were 9.1%(1/22) in the lesions less than 20mm in diameter, 30.0%(6/20) in the lesions with 20-30mm in diameter, 50.0%(2/4) in the lesions larger than 30mm in diameter. 8) Malignancy rates according to their morphologic types were 11.8%(2/17) in GH type, 21.4%(3/14) in NM type and 26.7%(4/15) in F type. Carcinoma invaded into the submucosa were present in one lesion of MN types and two of F type. Conclusions : LSTs larger than 20mm in diameter had high malgnant potential, which was more than 30%. Furthermore, LSTs showed different clinicopathologic characteristics depending on the morphologic classification. MN or F type LSTs had higher malignant potential than GH type.